A. We Need the Zerotime limit per test1 secondmemory limit per test256 megabytesinputstandard inputoutputstandard outputThere is an array a consisting of non-negative integers. You can choose an integer x and denote b_i=a_i \oplus x for all 1 \le i \le n, where \oplus denotes the bitwise XOR operation. Is it possible to choose such a number x that the value of the expression b_1 \oplus b_2 \oplus \ldots \oplus b_n equals 0?It can be shown that if a valid number x exists, then there also exists x such that (0 \le x < 2^8).InputEach test contains multiple test cases. The first line contains the number of test cases t (1 \le t \le 1000). The description of the test cases follows.The first line of the test case contains one integer n (1 \le n \le 10^3) — the length of the array a.The second line of the test case contains n integers — array a (0 \le a_i < 2^8).It is guaranteed that the sum of n over all test cases does not exceed 10^3.OutputFor each set test case, print the integer x (0 \le x < 2^8) if it exists, or -1 otherwise.ExampleInput
531 2 531 2 340 1 2 341 2 2 311Output
6
0
3
-1
1
NoteIn the first test case, after applying the operation with the number 6 the array b becomes [7, 4, 3], 7 \oplus 4 \oplus 3 = 0.There are other answers in the third test case, such as the number 0. 
531 2 531 2 340 1 2 341 2 2 311
6 0 3 -1 1 
['bitmasks', 'brute force', '*800']