// Arup Guha
// 11/2/2013
// Solution to 2013 South East Regional Division 2 Problem B: Christmas

import java.util.*;

public class christmas {

	final static int MAX = 1000001;

	public static void main(String[] args) {

		// Store all answers here.
		long[] ans = new long[MAX];
		ans[1] = 1;

		// Just add the total for day i to the previous day's total.
		long total = 1;
		for (int i=2; i<MAX; i++) {
			total += i;
			ans[i] = ans[i-1] + total;
		}

		Scanner stdin = new Scanner(System.in);
		int n = stdin.nextInt();

		// Process all cases.
		while (n != 0) {
			System.out.println(ans[n]);
			n = stdin.nextInt();
		}
	}
}