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 = sys.stdin.readline
  
  def main():
      n = int(input())
      alst = list(map(int, input().split()))
      pos = [-1] * n
      for i, a in enumerate(alst):
          a -= 1
          alst[i] -= 1
          if (a - i) % 2 == 1:
              print(-1)
              return
          pos[a] = i
      ans = []
      for i in range(n - 1, 0, -2):
          p = pos[i]
          ans.append(p + 1)
          for j in range(p // 2):
              alst[j], alst[p - j] = alst[p - j], alst[j]
              pos[alst[j]], pos[alst[p - j]] = pos[alst[p - j]], pos[alst[j]] 
          p = pos[i - 1]
          ans.append(p)
          p -= 1
          for j in range(p // 2):
              alst[j], alst[p - j] = alst[p - j], alst[j]
              pos[alst[j]], pos[alst[p - j]] = pos[alst[p - j]], pos[alst[j]] 
          ans.append(p + 3)
          p += 2
          for j in range(p // 2):
              alst[j], alst[p - j] = alst[p - j], alst[j]
              pos[alst[j]], pos[alst[p - j]] = pos[alst[p - j]], pos[alst[j]] 
          p = 2
          ans.append(3)
          for j in range(p // 2):
              alst[j], alst[p - j] = alst[p - j], alst[j]
              pos[alst[j]], pos[alst[p - j]] = pos[alst[p - j]], pos[alst[j]]
          p = i
          ans.append(p + 1)
          for j in range(p // 2):
              alst[j], alst[p - j] = alst[p - j], alst[j]
              pos[alst[j]], pos[alst[p - j]] = pos[alst[p - j]], pos[alst[j]]
  
      print(len(ans))
      print(*ans)
      
  for _ in range(int(input())):
      main()