#include <bits/stdc++.h>
using namespace std;

int main()
{
    long long N;
    cin >> N;
    int ans = 0;
    for (int i = 1; i <= 99999; i++)
    {
        string S;
        for (int j = 0; j < 3; j++)
        {
            S += to_string(i);
        }
        if (stoll(S) <= N)
        {
            ans++;
        }
    }
    cout << ans;
}