You have $$$n$$$ numbers $$$a_1, a_2, \ldots, a_n$$$. You want to arrange them in a circle so as to maximize the sum of products of pairs of adjacent numbers.
Formally, you want to find a permutation $$$b_1, b_2, \ldots, b_n$$$ of $$$a_1, a_2, \ldots, a_n$$$ such that $$$b_1b_2 + b_2b_3 + \ldots + b_{n-1}b_n + b_nb_1$$$ is maximal.
Find this maximum value.
The first line contains a single integer $$$t$$$ ($$$1 \le t \le 10^4$$$) — the number of test cases. The description of test cases follows.
The first line of each test case contains a single integer $$$n$$$ $$$(3 \le n \le 2\cdot 10^5)$$$ — the number of numbers.
The second line of each test case contains $$$n$$$ integers $$$a_1, a_2, \ldots, a_n$$$ ($$$-10^6 \le a_i \le 10^6$$$).
It is guaranteed that the sum of $$$n$$$ over all test cases does not exceed $$$2\cdot 10^5$$$.
For each test case, print a single integer — the maximum possible value of the expression $$$b_1b_2 + b_2b_3 + \ldots + b_{n-1}b_n + b_nb_1$$$ over all permutations $$$b_1, b_2, \ldots, b_n$$$ of $$$a_1, a_2, \ldots, a_n$$$.
431 2 361 1 1 1 0 05100000 100000 100000 100000 -10000051 2 3 4 5
11 3 10000000000 48
In the first test case, there is only one way to arrange the numbers in a circle (not counting rotations and symmetries) — $$$(1, 2, 3)$$$. The sum of products of pairs of adjacent numbers is $$$1\cdot 2 + 2\cdot 3 + 3\cdot 1 = 11$$$.
In the second test case, one of the optimal arrangements is $$$(1, 1, 1, 1, 0, 0)$$$. For it this sum is equal to $$$1 \cdot 1 + 1 \cdot 1 + 1 \cdot 1 + 1 \cdot 0 + 0 \cdot 0 + 0 \cdot 1 = 3$$$.
In the third test case, there is a unique (up to rotations and symmetries) way to arrange the numbers in a circle: $$$(100000, 100000, 100000, 100000, -100000)$$$, the answer is $$$100000^2 = 10^{10}$$$. Note that the answer may not fit into int32.
In the fourth test case, one of the optimal permutations is $$$(1, 2, 4, 5, 3)$$$, the answer for which is $$$1 \cdot 2 + 2 \cdot 4 + 4 \cdot 5 + 5 \cdot 3 + 3 \cdot 1 = 2 + 8 + 20 + 15 + 3 = 48$$$.
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