Akbar teacher

Input

The first line contains a single integer $t$ (1\le t \le 10 ^ 4) — the number of test cases.

The only line of each test case contains two integers $a,b$ (1 \le a ,b \le 1000) — the number of pencils that Fateh has and the number of pencils that Osman has.

Output

Print the game's result. If there is no solution to the game, print $-1$.

Examples

Note

In the first test case, Fateh has $3$ pencils and Osman has also $3$ pencils, so they do not have to share pencils because they already have the same amount of pencils.

In the second test case, it can be shown that there is no solution for that game.

Scoring

1. Subtask $1$ ($10$ points): (a=b)

2. Subtask $2$ ($40$ points) : No additional constraints