#include <bits/stdc++.h>
#define For(i, a, b) for(long long i = a; i < b; i++)
#define rep(i, n) For(i, 0, n)
#define rFor(i, a, b) for(long long i = a; i >= b; i--)
#define ALL(v) (v).begin(), (v).end()
#define rALL(v) (v).rbegin(), (v).rend()
using namespace std;

using lint = long long;
using ld = long double;

int main() {
    int d;
    cin >> d;
    int h = d / 2;
    int ans = 0;
    rep(i, h + 1) {
        ans = max(ans, (int)(i * (h - i)));
    }
    cout << ans << endl;
}