View Code of Problem 3689

import java.util.Scanner;
import java.math.BigInteger;

public class Main
{
  	public static void main(String[] args)
        {
          Scanner input=new Scanner(System.in);
          int i=input.nextInt();
          for(int t=0;t<i;t++)
          {
            BigInteger a=input.nextBigInteger();
            BigInteger b=input.nextBigInteger();
            System.out.println("Case #"+(t+1)+":");
            System.out.println(a.subtract(b));
          }
        }
}