백준 8393번

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);

    }
}