#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

int main() {
    int L; cin >> L;
    int a = L / 2 + 1, b = L / 2;
    cout << 1LL * a * ~-a / 2 + 1LL * b * ~-b / 2 << endl;
    return 0;
}