#include <iostream>
using namespace std;

int main() {

    int n;
    cin >> n;
    int sum = 0;

    // write your code here......
    if (n % 2 == 1) {
        n--;
    }

    sum = (n / 2) * (n / 2 + 1);

    cout << sum << endl;

    return 0;
}