D. Constant Palindrome Sumtime limit per test1 secondmemory limit per test256 megabytesinputstandard inputoutputstandard outputYou are given an array a consisting of n integers (it is guaranteed that n is even, i.e. divisible by 2). All a_i does not exceed some integer k.Your task is to replace the minimum number of elements (replacement is the following operation: choose some index i from 1 to n and replace a_i with some integer in range [1; k]) to satisfy the following conditions:  after all replacements, all a_i are positive integers not greater than k;  for all i from 1 to \frac{n}{2} the following equation is true: a_i + a_{n - i + 1} = x, where x should be the same for all \frac{n}{2} pairs of elements. You have to answer t independent test cases.InputThe first line of the input contains one integer t (1 \le t \le 10^4) — the number of test cases. Then t test cases follow.The first line of the test case contains two integers n and k (2 \le n \le 2 \cdot 10^5, 1 \le k \le 2 \cdot 10^5) — the length of a and the maximum possible value of some a_i correspondingly. It is guratanteed that n is even (i.e. divisible by 2). The second line of the test case contains n integers a_1, a_2, \dots, a_n (1 \le a_i \le k), where a_i is the i-th element of a.It is guaranteed that the sum of n (as well as the sum of k) over all test cases does not exceed 2 \cdot 10^5 (\sum n \le 2 \cdot 10^5, \sum k \le 2 \cdot 10^5).OutputFor each test case, print the answer — the minimum number of elements you have to replace in a to satisfy the conditions from the problem statement.ExampleInput
4
4 2
1 2 1 2
4 3
1 2 2 1
8 7
6 1 1 7 6 3 4 6
6 6
5 2 6 1 3 4
Output
0
1
4
2

4
4 2
1 2 1 2
4 3
1 2 2 1
8 7
6 1 1 7 6 3 4 6
6 6
5 2 6 1 3 4

0 1 4 2 
['brute force', 'data structures', 'greedy', 'two pointers', '*1700']