Got the answer!

Try the followig code and it will pass all test cases too

import java.io.; import java.util.; import java.text.; import java.math.; import java.util.regex.*;

public class Solution {

public static void main(String[] args) {

     Scanner sc = new Scanner(System.in);
     BigInteger bi1 = new BigInteger(sc.next());
     BigInteger bi2 = new BigInteger(sc.next());

        BigInteger  bi3, bi4;
        bi3 = bi1.add(bi2);
        bi4 = bi1.multiply(bi2);
        System.out.println( bi3);
        System.out.println( bi4);


}

}