#include <bits/stdc++.h>
int f(int x) { return 1 + std::min(abs(0 - x), std::abs(2000 - x)); }
int main() {
  int n;
  while (std::cin >> n) {
    int comb = 0;
    for (int i = 0; i <= 2000; ++i) {
      int list[2] = {};
      int x0 = i;
      int x1 = n - x0;
      if (x1 < 0) {
        continue;
      }
      comb += f(x0) * f(x1);
    }
    std::cout << comb << std::endl;
  }
  return 0;
}
