Many Perfect Squares

4000ms

524288K

Description:

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 $$$0, 1, 4, 9, 16, \ldots$$$.

Input:

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

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

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

It is guaranteed that the sum of $$$n$$$ over all test cases does not exceed $$$50$$$.

Output:

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 $$$0 \le x \le 10^{18}$$$.

Sample Input:

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

Sample Output:

Note:

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.

Informação

Provedor Codeforces

Código CF1781D