You are given two integers (a) and (b). You are to perform the following procedure: First, you choose an integer (k) such that (b) is divisible by (k). Then, you simultaneously multiply (a) by (k) and divide (b) by (k). Find the greatest possible even value of (a+b). If it is impossible to make (a+b) even, output (-1) instead. Each test contains multiple test cases. The first line contains the number of test cases (t) ((1 \le t \le 10^4)). The description of the test cases follows. The first line of each test case contains two integers (a) and (b) ((1 \leq a,b \leq a\cdot b \leq 10^{18})). For each test case, output the maximum even value of (a+b) on a new line. In the first test case, it can be shown it is impossible for (a+b) to be even. In the second test case, the optimal (k) is (2). The sum is (2+4=6).