#include<iostream>
using namespace std;

int ans;

void dfs(int m){
	
	int i;
	ans++;

	//m变成1的时候不进入循环跳出递归 
	for(i=1;i<=m/2;i++)
		dfs(i);
}

int main(){
	
	int n;
	cin>>n;
	dfs(n);
	cout<<ans - 1;
	return 0;
}

/**************************************************************
	Problem: 1307
	User: admin
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/