#include <iostream>
#include <sstream>
#include <math.h>
#include <stack>
#include <set>
#include <algorithm>
#include <string>
#include <queue>
#include <stack>
#include <map>
#include <cstdio>
#include <vector>
using namespace std;

#define INF (1 << 30)
#define INFLL (1LL << 60)

int main() {
	int s;
	cin >> s;
	long long int now = s/2;
	long long int ans = 0;
	while(now > 0){
		ans += now + now - 1;
		now--;
	}
	cout << ans << endl;
	return 0;
}