#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
using ll = long long;

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

    int ret = 0;
    for (int i = 1; i * 2 < d; i++) {
        ret = max(ret, i * ((d - i * 2) / 2));
    }

    cout << ret << endl;
    return 0;
}