#include<map>
#include<set>
#include<list>
#include<cmath>
#include<queue>
#include<stack>
#include<cstdio>
#include<string>
#include<vector>
#include<complex>
#include<cstdlib>
#include<cstring>
#include<numeric>
#include<sstream>
#include<iostream>
#include<algorithm>
#include<functional>

#define mp       make_pair
#define pb       push_back
#define all(x)   (x).begin(),(x).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,b,n) for(int i=b;i<n;i++)

using namespace std;

typedef    long long          ll;
typedef    unsigned long long ull;
typedef    vector<bool>       vb;
typedef    vector<int>        vi;
typedef    vector<vb>         vvb;
typedef    vector<vi>         vvi;
typedef    pair<int,int>      pii;

const int INF=1<<29;
const double EPS=1e-9;

const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};

int main(){
	int sum[2010];
	for(int i=0;i <=1000;i++){
		for(int j=0;j <=1000;j++){
			sum[i+j]++;
		}
	}
	int n;
	while(scanf("%d",&n)!=EOF){
		ll ans=0;
		for(int i=0;i <=2000;i++){
			int a =n-i;
			if(a<0)break;
			if(a>2000)continue;
			ans +=sum[i]*sum[a];
		}
		cout <<ans<<endl;
	}
	return 0;
}