D1. All are Sametime limit per test1 secondmemory limit per test256 megabytesinputstandard inputoutputstandard outputThis problem is a simplified version of D2, but it has significant differences, so read the whole statement.Polycarp has an array of n (n is even) integers a_1, a_2, \dots, a_n. Polycarp conceived of a positive integer k. After that, Polycarp began performing the following operations on the array: take an index i (1 \le i \le n) and reduce the number a_i by k.After Polycarp performed some (possibly zero) number of such operations, it turned out that all numbers in the array became the same. Find the maximum k at which such a situation is possible, or print -1 if such a number can be arbitrarily large.InputThe first line contains one integer t (1 \le t \le 10) — the number of test cases. Then t test cases follow.Each test case consists of two lines. The first line contains an even integer n (4 \le n \le 40) (n is even). The second line contains n integers a_1, a_2, \dots a_n (-10^6 \le a_i \le 10^6).It is guaranteed that the sum of all n specified in the given test cases does not exceed 100.OutputFor each test case output on a separate line an integer k (k \ge 1) — the maximum possible number that Polycarp used in operations on the array, or -1, if such a number can be arbitrarily large.ExampleInput
3
6
1 5 3 1 1 5
8
-1 0 1 -1 0 1 -1 0
4
100 -1000 -1000 -1000
Output
2
1
1100

3
6
1 5 3 1 1 5
8
-1 0 1 -1 0 1 -1 0
4
100 -1000 -1000 -1000

2 1 1100 
['math', 'number theory', '*1100']