2025. N줄덧셈.D1

import java.util.Scanner;
 
public class Solution {
 
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int sum=0;
        for(int i=n;i>0;i--) {
            sum+=i;
        }
        System.out.println(sum);
    }
 
}