#include <bits/stdc++.h>
using namespace std;
vector<int> v;
int a[2001];
int main() {
  for (int i = 0; i <= 1000; i++) {
    for (int j = 0; j <= 1000; j++) {
      a[i + j]++;
    }
  }
  int n;
  while (~scanf("%d", &n)) {
    int res = 0;
    for (int i = 0; i <= n; i++) {
      res += a[i] * a[n - i];
    }
    printf("%d\n", res);
  }
}
