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