#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int d;
  cin >> d;
  int x = d / 4;
  int y = x;
  while (x * 2 + (y + 1) * 2 <= d) ++y;
  cout << x * y << endl;
  return 0;
}