#include<iostream>
#include<sstream>
#include<algorithm>
#include<set>
#include<map>
#include<queue>
#include<complex>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cassert>

#define rep(i,n) for(int i=0;i<(int)n;i++)
#define all(c) (c).begin(),(c).end()
#define mp make_pair
#define pb push_back
#define each(i,c) for(__typeof((c).begin()) i=(c).begin();i!=(c).end();i++)
#define dbg(x) cerr<<__LINE__<<": "<<#x<<" = "<<(x)<<endl

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pi;
const int inf = (int)1e9;
const double INF = 1e12, EPS = 1e-9;

int n, dp[4010];

int main(){
	rep(i, 1001) rep(j, 1001) dp[i + j]++;
	
	while(cin >> n){
		
		ll ans = 0;
		rep(i, n + 1) ans += (ll)dp[i] * dp[n - i];
		cout << ans << endl;
	}
	return 0;
}