pat 甲级1001

import java.util.Scanner;
 
public class Main {
    public static void main(String[] args)  {
        Scanner scan = new Scanner(System.in);
        int a = scan.nextInt();
        int b = scan.nextInt();
        String str = "" + (a + b);
        int modOffset=str.length()%3;
        char[] chars=str.toCharArray();
        for(int i=0;i<chars.length;i++){
            if (chars[i]=='-'){
                System.out.print("-");
                continue;
            }
            System.out.print(chars[i]-48);
            if (i==chars.length-1){
                System.out.println();
            }else if ((i+1)%3==modOffset){
                System.out.print(",");
            }
        }
    }
}

思路取自柳神，我建议所有在刷pat的朋友都要去她那里看看，代码太漂亮了！