#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <iostream>
#include <map>
#include <list>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <queue>
#include <iomanip>

using namespace std;

int main(void)
{
	long long L;
	long long n;
	long long res = 0;

	cin >> L;

	n = L / 2;

	res += n * (n + 1) / 2;
	res += n * (n - 1) / 2;
	
	cout << res << endl;

	return (0);
}