#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<vector>
#include<queue>
using namespace std;

#define X first
#define Y second

typedef pair<int,int> pii;
typedef long long LL;
const char nl = '\n';
const int N = 1e6+10;
const int M = 1e6+10;
LL n,m;

void solve(){
	cin >> n;
    LL ans = 0;
    while(n>2){
=		n = n / 2 + 1;
		ans ++;
    }
    cout << ans;
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);

	solve();
}