#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000

int main(){
	
	long long L;
	cin>>L;
	long long n = L/2;
	L--;
	L/=2;
	
	cout<<n*L<<endl;
	
	return 0;
}