#include <iostream>
#include <stdio.h>
using namespace std;

int main() {
   int n,s,i;
   while(cin >> n) {
	   s=0;
	   i= n>2000 ? n-2000 : 0;
	   for (i;i<=n;i++) s=s+(i+1)*(n-i+1);
	   cout << s << endl;
   }
   return 0;
}