백준 #5341번 Pyramids

import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		
		int a = sc.nextInt();
		
		while(a != 0) {
			int count = 0;
			for(int i = 1; i <= a; i++) {
				count += i;
			}
			System.out.println(count);
			a = sc.nextInt();
		}
		sc.close();
	}
}