#P1781D. Many Perfect Squares

    ID: 331 Type: RemoteJudge 4000ms 512MiB Tried: 0 Accepted: 0 Difficulty: 6 Uploaded By: Tags>brute forcemathnumber theory*1800

Many Perfect Squares

Description

You are given a set a1,a2,,ana_1, a_2, \ldots, a_n of distinct positive integers.

We define the squareness of an integer xx as the number of perfect squares among the numbers a1+x,a2+x,,an+xa_1 + x, a_2 + x, \ldots, a_n + x.

Find the maximum squareness among all integers xx between 00 and 101810^{18}, inclusive.

Perfect squares are integers of the form t2t^2, where tt is a non-negative integer. The smallest perfect squares are 0,1,4,9,16,0, 1, 4, 9, 16, \ldots.

Each test contains multiple test cases. The first line contains the number of test cases tt (1t501 \le t \le 50). The description of the test cases follows.

The first line of each test case contains a single integer nn (1n501 \le n \le 50) — the size of the set.

The second line contains nn distinct integers a1,a2,,ana_1, a_2, \ldots, a_n in increasing order (1a1<a2<<an1091 \le a_1 < a_2 < \ldots < a_n \le 10^9) — the set itself.

It is guaranteed that the sum of nn over all test cases does not exceed 5050.

For each test case, print a single integer — the largest possible number of perfect squares among a1+x,a2+x,,an+xa_1 + x, a_2 + x, \ldots, a_n + x, for some 0x10180 \le x \le 10^{18}.

Input

Each test contains multiple test cases. The first line contains the number of test cases tt (1t501 \le t \le 50). The description of the test cases follows.

The first line of each test case contains a single integer nn (1n501 \le n \le 50) — the size of the set.

The second line contains nn distinct integers a1,a2,,ana_1, a_2, \ldots, a_n in increasing order (1a1<a2<<an1091 \le a_1 < a_2 < \ldots < a_n \le 10^9) — the set itself.

It is guaranteed that the sum of nn over all test cases does not exceed 5050.

Output

For each test case, print a single integer — the largest possible number of perfect squares among a1+x,a2+x,,an+xa_1 + x, a_2 + x, \ldots, a_n + x, for some 0x10180 \le x \le 10^{18}.

Sample Input 1

4
5
1 2 3 4 5
5
1 6 13 22 97
1
100
5
2 5 10 17 26

Sample Output 1

2
5
1
2

Note

In the first test case, for x=0x = 0 the set contains two perfect squares: 11 and 44. It is impossible to obtain more than two perfect squares.

In the second test case, for x=3x = 3 the set looks like 4,9,16,25,1004, 9, 16, 25, 100, that is, all its elements are perfect squares.