#include <bits/stdc++.h>

#define rep(i, n) for (int (i) = 0; (i) < (int)(n); (i)++)

const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, 1, 0, -1};
using namespace std;
typedef long long ll;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll L;
    cin >> L;
    ll p = L/2;
    cout << p*p << endl;
    return 0;
}