B'You are given a set a_1, a_2, ldots, a_n of distinct positive integers. We define the squareness of an integer x as the number of perfect squares among the numbers a_1 + x, a_2 + x, ldots, a_n + x . Find the maximum squareness among all integers x between 0 and 10^{18} , inclusive. Perfect squares are integers of the form t^2 , where t is a non-negative integer. The smallest perfect squares are 0, 1, 4, 9, 16, ldots . Each test contains multiple test cases. The first line contains the number of test cases t ( 1 <= t <= 50 ). The description of the test cases follows. The first line of each test case contains a single integer n ( 1 <= n <= 50 ) -- the size of the set. The second line contains n distinct integers a_1, a_2, ldots, a_n in increasing order ( 1 <= a_1 < a_2 < ldots < a_n <= 10^9 ) -- the set itself. It is guaranteed that the sum of n over all test cases does not exceed 50 . For each test case, print a single integer -- the largest possible number of perfect squares among a_1 + x, a_2 + x, ldots, a_n + x , for some 0 <= x <= 10^{18} . In the first test case, for x = 0 the set contains two perfect squares: 1 and 4 . It is impossible to obtain more than two perfect squares. In the second test case, for x = 3 the set looks like 4, 9, 16, 25, 100 , that is, all its elements are perfect squares. '...