#include <bits/stdc++.h> using namespace std; int main() { int n; cin>>n; int sum = 0; for(int i = 1;i <= n;i++) { int temp = 0; int number = i; while(number != 0) { temp = number % 10; if(temp == 1) { sum++; } number /= 10; } } cout<<sum; return 0; }