[입출력] 백준 8393

import java.util.Scanner;

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