#include<bits/stdc++.h>
using namespace std;
int n,ans;
void f(int x){
	for(int i=1;i<=x/2;i++){
		//1 2 3
		ans++;
		f(i);
	}		
}
int main(){
	cin>>n;
	f(n);


	return 0;
}



/**************************************************************
	Problem: 1307
	User: admin
	Language: C++
	Result: Wrong Answer
****************************************************************/