#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
// #include <bits/stdc++.h>
using namespace std;

int ban(int m) {
	int k;
	if (m / 2 < 1)
		return m;
	else {
		m /= 2;
		k = ban(m);
		return k+1;
	}
}

int main() {

	int n;
	cin >> n;

	int count = 0;

	count = ban(n);
	if (n == pow(2,(count - 1))) 
		count--;

	cout << count << endl;

	return 0;

}