#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)s; i < (int)e; ++i)
#define all(a) (a).begin(), (a).end()

int main() {
    cin.tie(nullptr);
    
    ll D;
    cin >> D;
    
    D /= 2;
    
    cout << (D / 2) * (D - D / 2) << '\n';
}