LCM calculation

Question

I wrote code for the problem given in spoj to calculate LCM. I calculated the gcd of 2 numbers and I divided the multiplication of 2 numbers with gcd which gives the lcm of 2 numbers, but it is showing wrong answer.

The problem is at http://www.spoj.com/problems/WPC5I/

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

class Lcm1 {
    public static void main(String args[]) throws Throwable {
        try {
            Scanner s = new Scanner(System.in);
            int siz = s.nextInt();
            for(int i = 0; i< siz; i++) {
                BigInteger a = s.nextBigInteger(), b = s.nextBigInteger();
                System.out.println((a.multiply(b)).divide(a.gcd(b)));
            }
        }
        catch(Exception e){}
    }
}