#include <iostream>
using namespace std;

int main() {
    int d;
    cin >> d;

    int ans = 0;
    if (d >= 4) {
        for (int h = 1; h < d / 2; h++) {
            int w = d / 2 - h;
            ans = max(ans, h * w);
        }
    }
    cout << ans << endl;
    return 0;
}