#include <bits/stdc++.h>   using namespace std;   long long const M = 2e5 + 10, M2 = 1e5 + 10, mod = 1e9 + 7, inf = 1e9 + 10;   int32_t main() {     ios::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     long long n;     cin >> n;     long long tmp = 1;     for (long long i = 1;; i++) {       if (tmp - 1 >= n) return cout << i - 1, 0;       tmp *= 2;     }   }   