[백준] #8393: 합

import java.util.Scanner;

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