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 random
  
  tc = int(input())
  while tc > 0:
      tc -= 1
      # n = 5
      n = int(input())
  
  
      def gen():
          even = list(range(0, n, 2))
          odd = list(range(1, n, 2))
          random.shuffle(even)
          random.shuffle(odd)
          return [odd[i // 2] if i % 2 else even[i // 2] for i in range(n)]
  
  
      a = list(map(lambda x: int(x) - 1, input().split()))
      # a = gen()
      if any((i + a[i]) % 2 for i in range(n)):
          print(-1)
      else:
          ans = []
  
  
          def rev(i):
              global a, ans
              assert i % 2 == 1 and i <= n
              a[:i] = a[i - 1::-1]
              ans += [i]
  
  
          for i in range(n - 2, -1, -2):
              while True:
                  if a[i] == i and a[i + 1] == i + 1:
                      break
                  if a[0] == i + 1 and a[1] == i:
                      rev(i + 2)
                  elif abs(a.index(i) - a.index(i + 1)) == 1:
                      rev(a.index(i) + 2)
                  elif a[0] == i + 1:
                      rev(a.index(i))
                  else:
                      rev(a.index(i + 1) + 1)
              assert all(j == a[j] for j in range(i, n))
          print(len(ans))
          print(*ans)
  