#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;

ll N, ans;
string S;

int main() {
  cin >> N;
  for (int i = 1; i <= 99999; i++) {
    S = to_string(i);
    S = S + S + S;
    if (stoll(S) <= N) ans++;
    else break;
  }
  cout << ans << endl;
  return 0;
}