#include <iostream>
#include <cstdint>

using namespace std;

int main() {

  ios::sync_with_stdio(false);
  cin.tie(0);

  int D;
  cin >> D;
  if (D & 1) {
    D = (D - 1) / 2;
    cout << ((D & 1) ? ((D >> 1) * ((D >> 1) + 1)) : ((D >> 1) * (D >> 1))) << endl;
  } else {
    D = D >> 1;
    cout << ((D & 1) ? ((D >> 1) * ((D >> 1) + 1)) : ((D >> 1) * (D >> 1))) << endl;
  }
}