输入：
-610
package com;import java.util.*;public class app4_8 {public static void main(String[] args){int n,i=1,sum=0;Scanner buf=new Scanner (System.in);do{System.out.println("输入正整数：");n=buf.nextInt();}while(n<0);while(i<=n)sum+=i++;System.out.println("1+2+...+"+n+"="+sum);}}
