#include <bits/stdc++.h>
using namespace std;
int ab[2050];
int main(void) {
  int n;
  for (int a = 0; a <= 1000; a++) {
    for (int b = 0; b <= 1000; b++) {
      ab[a + b]++;
    }
  }
  while (cin >> n) {
    if (cin.eof()) break;
    int ret = 0;
    for (int cd = 0; cd <= 2000; cd++) {
      if (n - cd >= 0) {
        ret += ab[cd] * ab[n - cd];
      }
    }
    cout << ret << endl;
  }
  return 0;
}
