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: from sys import stdin, stdout
  
  
  #  x x 9 x x x x
  #  9 x x x x 8 x
  #  x x x x 9 8 x
  #  x 8 9 x x x x
  #  9 8 x x x x x
  #  x x x x x 8 9
  
  def solve(n, a_a):
      p_a = [-1] * n
      for i in range(n):
          a_a[i] -= 1
          p_a[a_a[i]] = i
          if (a_a[i]) % 2 != i % 2:
              return [-1]
  
      res = []
      for i in range(n//2, 0, -1):
          cur = i*2
  
          # reverse cur to head
          res.append(p_a[cur]+1)
          reverse(a_a, p_a, p_a[cur])
  
          # reverse cur before smaller one
          res.append(p_a[cur-1])
          reverse(a_a, p_a, p_a[cur-1]-1)
  
          # reverse after smaller one
          res.append(p_a[cur-1]+2)
          reverse(a_a, p_a, p_a[cur - 1] + 1)
  
          # reverse cur to head
          res.append(p_a[cur] + 1)
          reverse(a_a, p_a, p_a[cur])
  
          # reverse cur to end
          res.append(cur + 1)
          reverse(a_a, p_a, cur)
  
      return [len(res), res]
  
  
  def reverse(a_a, p_a, i):
      l = 0
      r = i
      while l < r:
          swap(a_a, l, r)
          swap(p_a, a_a[l], a_a[r])
          l += 1
          r -= 1
  
  
  def swap(a_a, i, j):
      tmp = a_a[i]
      a_a[i] = a_a[j]
      a_a[j] = tmp
  
  
  t = int(stdin.readline())
  for _ in range(t):
      n = int(stdin.readline())
      a_a = list(map(int, stdin.readline().split()))
      res = solve(n, a_a)
      stdout.write(str(res[0]) + '\n')
      if res[0] > 0:
          stdout.write(' '.join(map(str, res[1])) + '\n')
  