#include<bits/stdc++.h>
using namespace std;
int main() 
{
    int n;
    cin >> n;
    int count = 0;
    for (int d = 1; d <= 9; d++) 
    {
        long long num = 0;
        for (int length = 1; length <= 4; length++)
        {
            num = num * 10 + d;
            if (num <= n) 
            {
                count++;
            } 
            else 
            {
                break;
            }
        }
    }
    cout << count << endl;
    return 0;
}