#include <iostream>
#include <vector>
#include <utility>
#include <set>
#include <list>
#include <cassert>
#include <queue>
#include <cmath>
#include <algorithm>

using namespace std;
using ll = long long int;
#define REP(i, n) for(int i = 0; i < (int)(n); i++)
#define YES(n) std::cout << ((n) ? "YES" : "NO"  ) << "\n";
#define Yes(n) std::cout << ((n) ? "Yes" : "No" ) << "\n";

#define ALL_INCLUDED_ENVIRONMENT

template <class T, class Alloc, template <class, class> class C> std::ostream& operator<<(std::ostream& o, const C<T, Alloc>& v) {
  o << "{";
  bool init = 1;
  for (auto e : v) {
    if (init) { init = 0; }
    else { o << ", "; }
    o << e;
  }
  o << "}";
  return o;
}

int int_width (ll x) {
  int ans = 0;
  while(x > 0) {
    x = x >> 1;
    ans++;
  }
  return ans;
}

int popcnt(uint64_t n)
{
    return __builtin_popcountll(n);
}

int tzcnt(uint64_t n)
{
    return n == 0 ? 64 : __builtin_ctzll(n);
}

int lzcnt(uint64_t n)
{
    return n == 0 ? 64 : __builtin_clzll(n);
}

int main() {
  // cin.tie(0);
  // ios::sync_with_stdio(false);
  ll n;
  cin >> n;
  ll ans = int_width(n);
  if (popcnt(n) == 1) ans--;
  cout << ans << "\n";
  return 0;
}