题解 | #小乐乐求和#

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