#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 = to_string(i);
    if (stoll(S + S + S) <= N){
      ans++;
    }
  }
  cout << ans << endl;
}