文件目录

#include <iostream>
using namespace std;
int main()
{
    int n;
    cin >> n;
    int ans = 0;
    for (int i = 1; i <= n; i++)
    {
        int m = i;
        while (m)
        {
            if (m % 10 == 1)
                ans++;
            m /= 10;
        }
    }
    cout << ans;
    return 0;
}