赛码在线编程1001

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		while (scanner.hasNext()) {
			int num = scanner.nextInt();
			int sum = 0;
			for (int i = 1; i <= num; i++) {
				sum += i;
			}
			System.out.println(sum);
			System.out.println();
		}
	}
}