CF2271A Robot Odd Moves

You are given a point $ (a, b) $ of the integer grid. A robot is standing at the point $ (0, 0) $ . The robot may perform the following two-step operation any number of times (possibly zero), where $ (x, y) $ denotes the point the robot is standing at: 1. Move one unit up or one unit down: $ (x, y) \rightarrow (x, y + 1) $ or $ (x, y) \rightarrow (x, y - 1) $ . 2. Then move one unit to the right: $ (x, y) \rightarrow (x + 1, y) $ . The robot visits a point if at some moment it is standing at this point: before the first operation, between the two moves of an operation, or after an operation. Find the minimum number of operations after which the robot has visited $ (a, b) $ , or determine that it is impossible.

Each test contains multiple test cases. The first line contains the number of test cases $ t $ ( $ 1 \le t \le 100 $ ). The description of the test cases follows. The only line of each test case contains two integers $ a $ and $ b $ ( $ 0 \le a, b \le 1000 $ ) — the coordinates of the given point.

For each test case, output a single integer — the minimum number of operations after which the robot has visited $ (a, b) $ , or $ -1 $ if it is impossible.

In the first example, the robot is standing at $ (0, 0) $ before the first operation, so it has already visited $ (0, 0) $ after $ 0 $ operations. In the second example, the robot moves up to $ (0, 1) $ and then right to $ (1, 1) $ during its first operation. Thus, it visits $ (0, 1) $ after $ 1 $ operation. In the third example, it can be proven that the robot cannot visit $ (0, 2) $ . In the fourth example, the robot can first move up and right, and then down and right. During the second operation, it visits $ (1, 0) $ . It cannot visit this point during the first operation, so the answer is $ 2 $ .