#include <iostream>
#include <cstring>

using namespace std;

int n;
int cnt[2020];

void setcnt() {
	memset(cnt, 0, sizeof(cnt));
	for (int i=0; i<=1000; i++) for (int j=0; j<=1000; j++) cnt[i+j]++;
}

void solve() {
	int ans = 0;
	for (int ab = 0; ab<=n; ab++) {
		ans += cnt[ab] * cnt[n-ab];
	}
	cout << ans << endl;
}

int main() {
	setcnt();
	
	while (cin>>n) {
		solve();
	}
	
	return 0;
}