#include<iostream>
using namespace std;
#define n 2021
#define c n-a-b
int main(){
  long long ans=0;
  for(int a=1;a<=n-4;a++){
    for(int b=1;b<=n-a-3;b++){
      ans+=(c-1)*(c-2)/2;
    }
  }
  cout<<ans;
  return 0;
}