#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  long long int ans[2001];
  long long int up = 6;
  ans[1] = 4;
  for (int i = 2; i < 2001; i++) {
    ans[i] += up + ans[i - 1];
    up += i + 2;
  }
  while (cin >> n) {
    if (n > 2000) {
      n -= 4000;
      n *= -1;
    }
    cout << ans[n] << endl;
  }
  return 0;
}
