BC146 添加逗号

import java.util.Scanner;// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {public static void main(String[] args) {Scanner in = new Scanner(System.in);String str = in.next();StringBuilder s = new StringBuilder(str);for(int index = s.length() - 3; index > 0;index -= 3  ) {s.insert(index,',');}System.out.println(s);}
}