[A,B입력=0]

 while(true) {
   System.out.print("A 입력>> ");
   int a = sc. nextInt();
   System.out.print("B 입력>> ");
   int b = sc. nextInt();
     if(a==0 && b==0) {
    	 break;	   
       }
   
   System.out.println("결과 >>"+(b-a));
   }