运行 ID: 8002

Main.cc: In function ‘int main()’:
Main.cc:8:10: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string’} and ‘int’)
    8 |      if(a==0){
      |         ~^~~
      |         |  |
      |         |  int
      |         std::string {aka std::__cxx11::basic_string}
In file included from /usr/include/c++/9/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
                 from Main.cc:1:
/usr/include/c++/9/bits/regex.h:1026:5: note: candidate: ‘template bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const std::__cxx11::sub_match<_BiIter>&)’
 1026 |     operator==(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/9/bits/regex.h:1026:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::__cxx11::sub_match<_BiIter>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
                 from Main.cc:1:
/usr/include/c++/9/bits/regex.h:1099:5: note: candidate: ‘template bool std::__cxx11::operator==(std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const std::__cxx11::sub_match<_BiIter>&)’
 1099 |     operator==(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/regex.h:1099:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   mismatched types ‘const std::__cxx11::sub_match<_BiIter>’ and ‘int’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
                 from Main.cc:1:
/usr/include/c++/9/bits/regex.h:1173:5: note: candidate: ‘template bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)’
 1173 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/regex.h:1173:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::__cxx11::sub_match<_BiIter>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
                 from Main.cc:1:
/usr/include/c++/9/bits/regex.h:1247:5: note: candidate: ‘template bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type*, const std::__cxx11::sub_match<_BiIter>&)’
 1247 |     operator==(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/regex.h:1247:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   mismatched types ‘const std::__cxx11::sub_match<_BiIter>’ and ‘int’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
                 from Main.cc:1:
/usr/include/c++/9/bits/regex.h:1321:5: note: candidate: ‘template bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)’
 1321 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/regex.h:1321:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::__cxx11::sub_match<_BiIter>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
                 from Main.cc:1:
/usr/include/c++/9/bits/regex.h:1395:5: note: candidate: ‘template bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type&, const std::__cxx11::sub_match<_BiIter>&)’
 1395 |     operator==(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/regex.h:1395:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   mismatched types ‘const std::__cxx11::sub_match<_BiIter>’ and ‘int’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
                 from Main.cc:1:
/usr/include/c++/9/bits/regex.h:1473:5: note: candidate: ‘template bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)’
 1473 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/regex.h:1473:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::__cxx11::sub_match<_BiIter>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
                 from Main.cc:1:
/usr/include/c++/9/bits/regex.h:1991:5: note: candidate: ‘template bool std::__cxx11::operator==(const std::__cxx11::match_results<_BiIter, _Alloc>&, const std::__cxx11::match_results<_BiIter, _Alloc>&)’
 1991 |     operator==(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/9/bits/regex.h:1991:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::__cxx11::match_results<_BiIter, _Alloc>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/iosfwd:40,
                 from /usr/include/c++/9/ios:38,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/bits/postypes.h:222:5: note: candidate: ‘template bool std::operator==(const std::fpos<_StateT>&, const std::fpos<_StateT>&)’
  222 |     operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/9/bits/postypes.h:222:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::fpos<_StateT>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:64,
                 from /usr/include/c++/9/bits/char_traits.h:39,
                 from /usr/include/c++/9/ios:40,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/bits/stl_pair.h:448:5: note: candidate: ‘template constexpr bool std::operator==(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)’
  448 |     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_pair.h:448:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::pair<_T1, _T2>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:67,
                 from /usr/include/c++/9/bits/char_traits.h:39,
                 from /usr/include/c++/9/ios:40,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/bits/stl_iterator.h:325:5: note: candidate: ‘template bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)’
  325 |     operator==(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_iterator.h:325:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::reverse_iterator<_Iterator>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:67,
                 from /usr/include/c++/9/bits/char_traits.h:39,
                 from /usr/include/c++/9/ios:40,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/bits/stl_iterator.h:363:5: note: candidate: ‘template bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&)’
  363 |     operator==(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_iterator.h:363:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::reverse_iterator<_Iterator>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:67,
                 from /usr/include/c++/9/bits/char_traits.h:39,
                 from /usr/include/c++/9/ios:40,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/bits/stl_iterator.h:1136:5: note: candidate: ‘template bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorR>&)’
 1136 |     operator==(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_iterator.h:1136:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::move_iterator<_IteratorL>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:67,
                 from /usr/include/c++/9/bits/char_traits.h:39,
                 from /usr/include/c++/9/ios:40,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/bits/stl_iterator.h:1142:5: note: candidate: ‘template bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorL>&)’
 1142 |     operator==(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_iterator.h:1142:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::move_iterator<_IteratorL>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/string:41,
                 from /usr/include/c++/9/bits/locale_classes.h:40,
                 from /usr/include/c++/9/bits/ios_base.h:41,
                 from /usr/include/c++/9/ios:42,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/bits/allocator.h:167:5: note: candidate: ‘template bool std::operator==(const std::allocator<_CharT>&, const std::allocator<_T2>&)’
  167 |     operator==(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/9/bits/allocator.h:167:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::allocator<_CharT>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/string:55,
                 from /usr/include/c++/9/bits/locale_classes.h:40,
                 from /usr/include/c++/9/bits/ios_base.h:41,
                 from /usr/include/c++/9/ios:42,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/bits/basic_string.h:6144:5: note: candidate: ‘template bool std::operator==(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)’
 6144 |     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/basic_string.h:6144:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   mismatched types ‘const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>’ and ‘int’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/string:55,
                 from /usr/include/c++/9/bits/locale_classes.h:40,
                 from /usr/include/c++/9/bits/ios_base.h:41,
                 from /usr/include/c++/9/ios:42,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/bits/basic_string.h:6152:5: note: candidate: ‘template typename __gnu_cxx::__enable_if::__value, bool>::__type std::operator==(const std::__cxx11::basic_string<_CharT>&, const std::__cxx11::basic_string<_CharT>&)’
 6152 |     operator==(const basic_string<_CharT>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/basic_string.h:6152:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   mismatched types ‘const std::__cxx11::basic_string<_CharT>’ and ‘int’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/string:55,
                 from /usr/include/c++/9/bits/locale_classes.h:40,
                 from /usr/include/c++/9/bits/ios_base.h:41,
                 from /usr/include/c++/9/ios:42,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/bits/basic_string.h:6166:5: note: candidate: ‘template bool std::operator==(const _CharT*, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)’
 6166 |     operator==(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/basic_string.h:6166:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   mismatched types ‘const _CharT*’ and ‘std::__cxx11::basic_string’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/string:55,
                 from /usr/include/c++/9/bits/locale_classes.h:40,
                 from /usr/include/c++/9/bits/ios_base.h:41,
                 from /usr/include/c++/9/ios:42,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/bits/basic_string.h:6178:5: note: candidate: ‘template bool std::operator==(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)’
 6178 |     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/basic_string.h:6178:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   mismatched types ‘const _CharT*’ and ‘int’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/bits/ios_base.h:46,
                 from /usr/include/c++/9/ios:42,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:292:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string’} to ‘const std::error_code&’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:297:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string’} to ‘const std::error_code&’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:304:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string’} to ‘const std::error_condition&’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  311 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:311:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string’} to ‘const std::error_condition&’
  311 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
                 from /usr/include/c++/9/istream:38,
                 from /usr/include/c++/9/sstream:38,
                 from /usr/include/c++/9/complex:45,
                 from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/bits/streambuf_iterator.h:208:5: note: candidate: ‘template bool std::operator==(const std::istreambuf_iterator<_CharT, _Traits>&, const std::istreambuf_iterator<_CharT, _Traits>&)’
  208 |     operator==(const istreambuf_iterator<_CharT, _Traits>& __a,
      |     ^~~~~~~~
/usr/include/c++/9/bits/streambuf_iterator.h:208:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::istreambuf_iterator<_CharT, _Traits>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/complex:463:5: note: candidate: ‘template constexpr bool std::operator==(const std::complex<_Tp>&, const std::complex<_Tp>&)’
  463 |     operator==(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/9/complex:463:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::complex<_Tp>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/complex:468:5: note: candidate: ‘template constexpr bool std::operator==(const std::complex<_Tp>&, const _Tp&)’
  468 |     operator==(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/9/complex:468:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::complex<_Tp>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
                 from Main.cc:1:
/usr/include/c++/9/complex:473:5: note: candidate: ‘template constexpr bool std::operator==(const _Tp&, const std::complex<_Tp>&)’
  473 |     operator==(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/9/complex:473:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   mismatched types ‘const std::complex<_Tp>’ and ‘int’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/deque:67,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:68,
                 from Main.cc:1:
/usr/include/c++/9/bits/stl_deque.h:286:5: note: candidate: ‘template bool std::operator==(const std::_Deque_iterator<_Tp, _Ref, _Ptr>&, const std::_Deque_iterator<_Tp, _Ref, _Ptr>&)’
  286 |     operator==(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_deque.h:286:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::_Deque_iterator<_Tp, _Ref, _Ptr>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/deque:67,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:68,
                 from Main.cc:1:
/usr/include/c++/9/bits/stl_deque.h:293:5: note: candidate: ‘template bool std::operator==(const std::_Deque_iterator<_Tp, _Ref, _Ptr>&, const std::_Deque_iterator<_Tp, _RefR, _PtrR>&)’
  293 |     operator==(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_deque.h:293:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::_Deque_iterator<_Tp, _Ref, _Ptr>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/deque:67,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:68,
                 from Main.cc:1:
/usr/include/c++/9/bits/stl_deque.h:2312:5: note: candidate: ‘template bool std::operator==(const std::deque<_Tp, _Alloc>&, const std::deque<_Tp, _Alloc>&)’
 2312 |     operator==(const deque<_Tp, _Alloc>& __x,
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_deque.h:2312:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::deque<_Tp, _Alloc>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/tuple:39,
                 from /usr/include/c++/9/functional:54,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:71,
                 from Main.cc:1:
/usr/include/c++/9/array:252:5: note: candidate: ‘template bool std::operator==(const std::array<_Tp, _Nm>&, const std::array<_Tp, _Nm>&)’
  252 |     operator==(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two)
      |     ^~~~~~~~
/usr/include/c++/9/array:252:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::array<_Tp, _Nm>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/functional:54,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:71,
                 from Main.cc:1:
/usr/include/c++/9/tuple:1419:5: note: candidate: ‘template constexpr bool std::operator==(const std::tuple<_Tps ...>&, const std::tuple<_Elements ...>&)’
 1419 |     operator==(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/9/tuple:1419:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::tuple<_Tps ...>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/functional:59,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:71,
                 from Main.cc:1:
/usr/include/c++/9/bits/std_function.h:746:5: note: candidate: ‘template bool std::operator==(const std::function<_Res(_ArgTypes ...)>&, std::nullptr_t)’
  746 |     operator==(const function<_Res(_Args...)>& __f, nullptr_t) noexcept
      |     ^~~~~~~~
/usr/include/c++/9/bits/std_function.h:746:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::function<_Res(_ArgTypes ...)>’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/functional:59,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:71,
                 from Main.cc:1:
/usr/include/c++/9/bits/std_function.h:752:5: note: candidate: ‘template bool std::operator==(std::nullptr_t, const std::function<_Res(_ArgTypes ...)>&)’
  752 |     operator==(nullptr_t, const function<_Res(_Args...)>& __f) noexcept
      |     ^~~~~~~~
/usr/include/c++/9/bits/std_function.h:752:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   mismatched types ‘const std::function<_Res(_ArgTypes ...)>’ and ‘int’
    8 |      if(a==0){
      |            ^
In file included from /usr/include/c++/9/bits/locale_conv.h:41,
                 from /usr/include/c++/9/locale:43,
                 from /usr/include/c++/9/iomanip:43,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:72,
                 from Main.cc:1:
/usr/include/c++/9/bits/unique_ptr.h:715:5: note: candidate: ‘template bool std::operator==(const std::unique_ptr<_Tp, _Dp>&, const std::unique_ptr<_Up, _Ep>&)’
  715 |     operator==(const unique_ptr<_Tp, _Dp>& __x,
      |     ^~~~~~~~
/usr/include/c++/9/bits/unique_ptr.h:715:5: note:   template argument deduction/substitution failed:
Main.cc:8:12: note:   ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::unique_ptr<_Tp, _Dp>’