#include <bits/stdc++.h>
using namespace std;

template <typename T, typename U> void cmin(T &a, U b) {
  if (a > b) a = b;
}
template <typename T, typename U> void cmax(T &a, U b) {
  if (a < b) a = b;
}

signed main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);

  long D;
  cin >> D;

  long mx = 0;
  for (long h = 0; h <= D / 2; h++) {
    long w = (D - h * 2) / 2;
    if (h < 0 || w < 0) continue;
    cmax(mx, h * w);
  }
  cout << mx << "\n";
}