description: You have a permutation: an array a = [a_1, a_2, …, a_n] of distinct integers from 1 to n. The length of the permutation n is odd.
  
  You need to sort the permutation in increasing order.
  
  In one step, you can choose any prefix of the permutation with an odd length and reverse it. Formally, if a = [a_1, a_2, …, a_n], you can choose any odd integer p between 1 and n, inclusive, and set a to [a_p, a_{p-1}, …, a_1, a_{p+1}, a_{p+2}, …, a_n].
  
  Find a way to sort a using no more than 5n/2 reversals of the above kind, or determine that such a way doesn't exist. The number of reversals doesn't have to be minimized.
  
  Input
  
  Each test contains multiple test cases. The first line contains the number of test cases t (1 ≤ t ≤ 100). Description of the test cases follows.
  
  The first line of each test case contains a single integer n (3 ≤ n ≤ 2021; n is odd) — the length of the permutation.
  
  The second line contains n distinct integers a_1, a_2, …, a_n (1 ≤ a_i ≤ n) — the permutation itself. 
  
  It is guaranteed that the sum of n over all test cases does not exceed 2021.
  
  Output
  
  For each test case, if it's impossible to sort the given permutation in at most 5n/2 reversals, print a single integer -1.
  
  Otherwise, print an integer m (0 ≤ m ≤ 5n/2), denoting the number of reversals in your sequence of steps, followed by m integers p_i (1 ≤ p_i ≤ n; p_i is odd), denoting the lengths of the prefixes of a to be reversed, in chronological order.
  
  Note that m doesn't have to be minimized. If there are multiple answers, print any.
  
  Example
  
  Input
  
  
  3
  3
  1 2 3
  5
  3 4 5 2 1
  3
  2 1 3
  
  
  Output
  
  
  4
  3 3 3 3
  2
  3 5
  -1
  
  Note
  
  In the first test case, the permutation is already sorted. Any even number of reversals of the length 3 prefix doesn't change that fact.
  
  In the second test case, after reversing the prefix of length 3 the permutation will change to [5, 4, 3, 2, 1], and then after reversing the prefix of length 5 the permutation will change to [1, 2, 3, 4, 5].
  
  In the third test case, it's impossible to sort the permutation.
solution: import sys
  input = lambda: sys.stdin.readline().rstrip()
  
  from random import shuffle
  T = int(input())
  for _ in range(T):
      def calcI():
          for i, a in enumerate(A):
              I[a] = i
      def addans(i):
          ANS.append(i)
          A[:i] = A[:i][::-1]
          calcI()
      
      N = int(input())
      A = [int(a) - 1 for a in input().split()]
      I = [0] * N
      k = (N - 1) // 2
      ng = 0
      for i, a in enumerate(A):
          if (i ^ a) & 1:
              ng = 1
              break
      if ng:
          print(-1)
          continue
      calcI()
      
      ANS = []
      while k:
          r = 2 * k
          l = r - 1
          if I[r] == r and I[l] == l:
              k -= 1
              continue
          if I[r] == 0 and I[l] == 1:
              addans(r + 1)
              k -= 1
              continue
          if I[r] - I[l] == 1:
              addans(I[r] + 1)
              continue
          if I[l] - I[r] == 1:
              addans(I[l] + 2)
              continue
          if I[r] == 0:
              addans(I[l])
              continue
          if I[l] > I[r]:
              addans(I[r] + 1)
              continue
          addans(I[r] + 1)
      if not ANS: ANS = [3, 3]
      print(len(ANS))
      print(*ANS)
  