#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <queue>
#include <stack>
#include <vector>
#include <algorithm>
#include <string>
#include <cstring>
#include <cmath>
#include <complex>
#include <map>
#include <climits>
#include <sstream>
using namespace std;
 
#define reep(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n) reep((i),0,(n))
#define ALL(v) (v).begin(),(v).end()
#define PB push_back
#define EPS 1e-8
#define F first
#define S second
#define mkp make_pair
 
static const double PI=6*asin(0.5);
typedef long long ll;
typedef complex<double> CP;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vint;
static const int INF=1<<24;
 
template <class T>
void initvv(vector<vector<T> > &v,int a,int b, const T  &t = T()){
    v.assign(a,vector<T>(b,t));
}
 
//v.erase(unique(v.begin(),v.end()),v.end());

int main(){
	int n;
	while(cin>>n){
		ll ans=0;
		int large=n;
		int small=max(n-1000,0);
		rep(i,1001){
			if(i>n) break;
			rep(j,1001){
				if(i+j>n) break;
				if(n-i+j>2000) break;
				int a=min(large-i-j,1000),b=max(small-i-j,0);
				if(a<0||b>1000) break;
				// cout<<a<<" "<<b<<" "<<i+j<<endl;
				ans+=(ll)a-b+1;
				
			}
		}
		cout<<ans<<endl;
	}
}

/*
10
20
8436
*/