import java.util.Scanner;
public class Luck{

public static void main(String[] args){   System.out.println("请输入您的4为会员卡号");     Scanner num = new Scanner(System.in);     int number = num.nextInt();     int a = number/1000; //千位     int b = number/1000/100; //百位     int c = number/100/10; //十位     int d = number/10; //个位     int e = a+b+c+d;     System.out.println(e); if(a+b+c+d>20){    System.out.println("中奖");

}

    else{    System.out.println("没中");

}

}     } 

假如我输入了5位数怎么写能通知出错并且提示？？？