#include <iostream> #include <string> using namespace std; bool is(int x) { string s = to_string(x); int n = s.length(); for (int i = 0; i < n / 2; ++i) { if (s[i]!= s[n - 1 - i]) { return false; } } return true; } int c(int n) { int count = 0; for (int i = 1; i <= n; ++i) { if (is(i)) { ++count; } } return count; } int main() { int n; cin >> n; cout << c(n) << endl; return 0; }