CF1698A.XOR Mixup

There is an array $a$ with $n-1$ integers. Let $x$ be the bitwise XOR of all elements of the array. The number $x$ is added to the end of the array $a$ (now it has length $n$ ), and then the elements are shuffled.

You are given the newly formed array $a$ . What is $x$ ? If there are multiple possible values of $x$ , you can output any of them.

The input consists of multiple test cases. The first line contains an integer $t$ ( $1 \leq t \leq 1000$ ) — the number of test cases. The description of the test cases follows.

The first line of each test case contains an integer $n$ ( $2 \leq n \leq 100$ ) — the number of integers in the resulting array $a$ .

The second line of each test case contains $n$ integers $a_1, a_2, \ldots, a_n$ ( $0 \le a_i \le 127$ ) — the elements of the newly formed array $a$ .

Additional constraint on the input: the array $a$ is made by the process described in the statement; that is, some value of $x$ exists.

For each test case, output a single integer — the value of $x$ , as described in the statement. If there are multiple possible values of $x$ , output any of them.

In the first test case, one possible array $a$ is $a=[2, 5, 4]$ . Then $x = 2 \oplus 5 \oplus 4 = 3$ ( $\oplus$ denotes the bitwise XOR), so the new array is $[2, 5, 4, 3]$ . Afterwards, the array is shuffled to form $[4, 3, 2, 5]$ .

In the second test case, one possible array $a$ is $a=[1, 10, 6, 10]$ . Then $x = 1 \oplus 10 \oplus 6 \oplus 10 = 7$ , so the new array is $[1, 10, 6, 10, 7]$ . Afterwards, the array is shuffled to form $[6, 1, 10, 7, 10]$ .

In the third test case, all elements of the array are equal to $6$ , so $x=6$ .

In the fourth test case, one possible array $a$ is $a=[100, 100]$ . Then $x = 100 \oplus 100 = 0$ , so the new array is $[100, 100, 0]$ . Afterwards, the array is shuffled to form $[100, 100, 0]$ . (Note that after the shuffle, the array can remain the same.)