so easy

Given an array with $$n$$ integers, assume $f(S)$ as the result of executing xor operation among all the elements of set $S$. e.g. if $S = \{1,2,3\}$ then $f(S) = 0$.

your task is: calculate xor of all $f(s)$, here $s \subseteq S$.

This problem has multi test cases. First line contains a single integer $T(T\leq 20)$ which represents the number of test cases.
For each test case, the first line contains a single integer number $n(1\leq n \leq 1,000)$ that represents the size of the given set. then the following line consists of $n$ different integer numbers indicate elements($\leq 10^9$) of the given set.

For each test case, print a single integer as the answer.

1
3
1  2  3

0

In the sample，$S = \{1, 2, 3\}$, subsets of $S$ are: $\varnothing$, {1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1, 2, 3}

BestCoder Round #77 (div.2)