#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n, a[1000000], b, c,sum;
    cin >> n;
    for(int i = 1;i <= n;i++)
    {
        a[i] = i;
    }
    sum = 0;
    for(int i = 1;i <= n;i++)
    {
        b = a[i];
        while (b > 0)
        {
            c = b % 10;
            if(c == 1)
            {
                sum += 1;
            }
            b = b / 10;
        }
    }
    cout << sum;
    return 0;
}