HZ is doing homework. The answer to a problem is three integers . After trying for several hours, he finally solved it. But unfortunately, he lost the value of by accident. Besides the values of and , he only remembers that and is a multiple of . But HZ is so tired that he doesn't want to solve the original problem again. Can you help him calculate the value of ?

输入描述:

The first line of input contains an integer  (), denoting the number of test cases.
Each test case contains two integers  and  in one line. .

输出描述:

For each test case, print one integer  in one line, denoting your answer.
Pay attention that your answer must satisfy  and  is a multiple of .
If there is no solution, print ``-1''. If there are multiple solutions, you can print any one of them.

2
1 2
666666 666666

999997
666668