#include<iostream>
#include<string>
#include<algorithm>
#include<map>
#include<set>
#include<utility>
#include<vector>
#include<cmath>
#include<cstdio>
#define loop(i,a,b) for(int i=a;i<b;i++) 
#define rep(i,a) loop(i,0,a)
#define pb push_back
#define mp make_pair
#define it ::iterator
#define all(in) in.begin(),in.end()
const double PI=acos(-1);
const double ESP=1e-10;
using namespace std;
int num[2001]={0};
int main(){
  int n;
  rep(i,1001)rep(j,1001)num[i+j]++;
  while(cin>>n){
    int ans=0;
    rep(i,2001){
      if(n-i<0)break;
      if(n-i>2000)continue;
      ans+=num[i]*num[n-i];
    }
    cout<<ans<<endl;
  }

}