You are given two positive integers (x) and (y) ((1\le x, y\le 10^9)). Find a non-negative integer (k\le 10^{18}), such that ((x+k) + (y+k) = (x+k)\oplus (y+k)) holds(^{\text{∗}}), or determine that such an integer does not exist. (^{\text{∗}})(\oplus) denotes the bitwise XOR operation . 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 only line of each test case contains two integers (x) and (y) ((1\le x, y\le 10^9)) — the given integers. For each test case, output a single integer (k) ((0\le k\le 10^{18})) — the integer you found. Print (-1) if it is impossible to find such an integer. If there are multiple answers, you may print any of them. In the first test case, since ((2 + 0) + (5 + 0) = (2 + 0) \oplus (5 + 0) = 7), (k=0) is a possible answer. Note that (k=4) is also a possible answer because ((2 + 4) + (5 + 4) = (2 + 4) \oplus (5 + 4) = 15). In the second test case, ((x+k)\oplus (y+k) = (6+k)\oplus (6+k) = 0). However, ((x+k)+(y+k) > 0) holds for every (k \ge 0), implying that such an integer (k) does not exist.