B"After winning another Bed Wars game, Masha and Olya wanted to relax and decided to play a new game. Masha gives Olya an array a of length n and a number s . Now Olya's task is to find a non-negative number x such that displaystyle sum_{i=1}^{n} a_i oplus x = s . But she is very tired after a tight round, so please help her with this. But this task seemed too simple to them, so they decided to make the numbers larger (up to 2^k ) and provide you with their binary representation. Each test consists of several test cases. The first line contains a single integer t ( 1 <= t <= 10^4 ) -- the number of test cases. Then follows the description of the test cases. The first line of each test case contains two integers n and k ( 1 <= n, k, n cdot k <= 2 cdot 10^6 ) -- the length of the array a and the length of the binary representation of all numbers. The second line contains a string of length k , consisting of zeros and ones -- the binary representation of the number s , starting from the most significant bits. The next n lines also contain strings of length k , consisting of zeros and ones, the i -th of these strings contains the binary representation of the number a_i , starting from the most significant bits. It is guaranteed that the sum of the values n cdot k for all test cases does not exceed 2 cdot 10^6 . For each test case, output a string of length k on a separate line, consisting of zeros or ones -- the binary representation of any suitable number x ( x ge 0 ), starting from the most significant bits, or -1 if such x does not exist. In the first test case, s = 11, a = [14, 6, 12, 15] , if x = 14 , then displaystyle sum_{i=1}^{n} a_i oplus x = (14 oplus 14) + (6 oplus 14) + (12 oplus 14) + (15 oplus 14) = 0 + 8 + 2 + 1 = 11 = s . In the second test case, s = 41, a = [191, 158] "...