#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int64_t N;
  cin >> N;
  int res = 0;
  for (int64_t i = 1; i < N; i *= 2) {
    res++;
  }
  cout << res << '\n';
  return 0;
}