Java 代码

import java.util.Scanner;

public class Main
{
    public static void main(String[] args)
    {
        Scanner cin = new Scanner(System.in);

        int a = cin.nextInt();

        int n = cin.nextInt();
        while (n <= 0)
        {
            n = cin.nextInt();
        }

        int sum = 0;

        for (int i = a; i < a + n; i ++)
            sum += i;

        System.out.println (sum);
    }
}