human
Among Johnny's numerous hobbies, there are two seemingly harmless ones: applying bitwise operations and sneaking into his dad's office. As it is usually the case with small children, Johnny is unaware that combining these two activities can get him in a lot of trouble.

There is a set S containing very important numbers on his dad's desk. The minute Johnny heard about it, he decided that it's a good idea to choose a positive integer k and replace each element s of the set S with s ⊕ k (⊕ denotes the [exclusive or](https://en.wikipedia.org/wiki/Exclusive_or#Computer_science) operation). 

Help him choose such k that Johnny's dad will not see any difference after his son is done playing (i.e. Johnny will get the same set as before playing). It is possible that no such number exists. It is also possible that there are many of them. In such a case, output the smallest one. Note that the order of elements in a set doesn't matter, i.e. set \{1, 2, 3\} equals to set \{2, 1, 3\}.

Formally, find the smallest positive integer k such that \\{s ⊕ k | s ∈ S\} = S or report that there is no such number.

For example, if S = \{1, 3, 4\} and k = 2, new set will be equal to \{3, 1, 6\}. If S = \{0, 1, 2, 3\} and k = 1, after playing set will stay the same.

Input

In the first line of input, there is a single integer t (1 ≤ t ≤ 1024), the number of test cases. In the next lines, t test cases follow. Each of them consists of two lines. 

In the first line there is a single integer n (1 ≤ n ≤ 1024) denoting the number of elements in set S. Second line consists of n distinct integers s_i (0 ≤ s_i < 1024), elements of S.

It is guaranteed that the sum of n over all test cases will not exceed 1024.

Output

Print t lines.
i-th line should contain the answer to the i-th test case, the minimal positive integer k satisfying the conditions or -1 if no such k exists.

Example

Input

6
4
1 0 2 3
6
10 7 14 8 3 12
2
0 2
3
1 2 3
6
1 4 6 10 11 12
2
0 1023

Output

1
4
2
-1
-1
1023

Note

In the first test case, the answer is 1 because...
 ... What is a Python program to find the smallest positive integer k such that \\{s ⊕ k | s ∈ S\} = S or report that there is no such number?
assistant
#Here is Python program to find the smallest positive integer k such that \\{s ⊕ k | s ∈ S\} = S or report that there is no such number.

from sys import stdin, stdout
from math import floor, gcd, fabs, factorial, fmod, sqrt, inf, log, ceil
from collections import defaultdict as dd, deque
from heapq import merge, heapify, heappop, heappush, nsmallest
from bisect import bisect_left as bl, bisect_right as br, bisect
        
mod = pow(10, 9) + 7
mod2 = 998244353
        
def inp(): return stdin.readline().strip()
def iinp(): return int(inp())
def out(var, end="\n"): stdout.write(str(var)+"\n")
def outa(*var, end="\n"): stdout.write(' '.join(map(str, var)) + end)
def lmp(): return list(mp())
def mp(): return map(int, inp().split())
def l1d(n, val=0): return [val for i in range(n)]
def l2d(n, m, val=0): return [l1d(m, val) for j in range(n)]
# def ceil(a,b): return (a+b-1)//b
S1 = 'abcdefghijklmnopqrstuvwxyz'
S2 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
def isprime(x):
    if x<=1: return False
    if x in (2, 3): return True
    if x%2 == 0: return False
    for i in range(3, int(sqrt(x))+1, 2):
        if x%i == 0: return False
    return True
 
for _ in range(int(inp())):
    n = iinp()
    arr = lmp()
    if max(arr) == 0:
        print(-1)
        continue
    mx = 1024
    flg = False
    sarr = sorted(arr)

    for i in range(1, mx+1):
        tmp = [i^x for x in arr]
        if sorted(tmp)==sarr:
            flg = True
            break

    print(i if flg else -1)