#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  while (cin >> n) {
    long long ans = 0;
    for (int cut = 0; cut <= n; cut++) {
      ans += min(cut + 1, 1001) * min(n - cut + 1, 1001);
    }
    cout << ans << endl;
  }
  return 0;
}
