#include <bits/stdc++.h>
using namespace std;
int memo[4][4001];
int rec(int idx, int left) {
  if (idx == 3) return (left <= 1000 ? 1 : 0);
  if (memo[idx][left] != -1) return memo[idx][left];
  int ans = 0;
  for (int i = 0; i <= min(1000, left); i++) {
    ans += rec(idx + 1, left - i);
  }
  return ans;
}
int main() {
  for (int n = 0; cin >> n;) {
    memset(memo, -1, sizeof memo);
    cout << rec(0, n) << endl;
  }
}
