A15602. Interesting Sequence

Petya and his friend, robot Petya++, like to solve exciting math problems.

One day Petya++ came up with the numbers $n$ and $x$ and wrote the following equality on the board: $$$$n\ \&\ (n+1)\ \&\ \dots\ \&\ m = x, $$ where $\\&amp;$ denotes the <a href="https://en.wikipedia.org/wiki/Bitwise_operation#AND">bitwise AND operation</a>. Then he suggested his friend Petya find such a minimal $m$ ( $m \\ge n$$$) that the equality on the board holds.

Unfortunately, Petya couldn't solve this problem in his head and decided to ask for computer help. He quickly wrote a program and found the answer.

Can you solve this difficult problem?


Each test contains multiple test cases. The first line contains the number of test cases $t$ ( $1 \le t \le 2000$ ). The description of the test cases follows.

The only line of each test case contains two integers $n$ , $x$ ( $0\le n, x \le 10^{18}$ ).

For every test case, output the smallest possible value of $m$ such that equality holds.

If the equality does not hold for any $m$ , print $-1$ instead.

We can show that if the required $m$ exists, it does not exceed $5 \cdot 10^{18}$ .

In the first example, $10\ \&\ 11 = 10$ , but $10\ \&\ 11\ \&\ 12 = 8$ , so the answer is $12$ .

In the second example, $10 = 10$ , so the answer is $10$ .

In the third example, we can see that the required $m$ does not exist, so we have to print $-1$ .