description: Paprika loves permutations. She has an array a_1, a_2, ..., a_n. She wants to make the array a permutation of integers 1 to n.
  
  In order to achieve this goal, she can perform operations on the array. In each operation she can choose two integers i (1 ≤ i ≤ n) and x (x > 0), then perform a_i := a_i mod x (that is, replace a_i by the remainder of a_i divided by x). In different operations, the chosen i and x can be different.
  
  Determine the minimum number of operations needed to make the array a permutation of integers 1 to n. If it is impossible, output -1.
  
  A permutation is an array consisting of n distinct integers from 1 to n in arbitrary order. For example, [2,3,1,5,4] is a permutation, but [1,2,2] is not a permutation (2 appears twice in the array) and [1,3,4] is also not a permutation (n=3 but there is 4 in the array).
  
  Input
  
  Each test contains multiple test cases. The first line contains a single integer t (1 ≤ t ≤ 10^4) — the number of test cases. Description of the test cases follows.
  
  The first line of each test case contains an integer n (1 ≤ n ≤ 10^5).
  
  The second line of each test case contains n integers a_1, a_2, ..., a_n. (1 ≤ a_i ≤ 10^9).
  
  It is guaranteed that the sum of n over all test cases does not exceed 2 ⋅ 10^5.
  
  Output
  
  For each test case, output the minimum number of operations needed to make the array a permutation of integers 1 to n, or -1 if it is impossible.
  
  Example
  
  Input
  
  
  4
  2
  1 7
  3
  1 5 4
  4
  12345678 87654321 20211218 23571113
  9
  1 2 3 4 18 19 5 6 7
  
  
  Output
  
  
  1
  -1
  4
  2
  
  Note
  
  For the first test, the only possible sequence of operations which minimizes the number of operations is: 
  
    * Choose i=2, x=5. Perform a_2 := a_2 mod 5 = 2. 
  
  
  
  For the second test, it is impossible to obtain a permutation of integers from 1 to n.
solution: inp = int(input())
  
  for i in range(inp):
      n = int(input())
      true_set = {}
      for i in range(1, n + 1):
          true_set[i] = 1
  
      false_set = list(map(int, input().split()))
      false_set.sort()
      ans = n
  
      new_false_set = []
  
      for i in range(1, n + 1):
          if false_set[i - 1] in true_set and true_set[false_set[i - 1]] != 0:
              true_set[false_set[i - 1]] = 0
              false_set[i - 1] = 0
              ans -= 1
          else:
              new_false_set.append(false_set[i - 1])
  
  
      new_true_set = []
      for i in true_set:
          if true_set[i] != 0:
              new_true_set.append(i)
  
  
      iter = 0
  
      for i in new_true_set:
          if new_false_set[iter] % 2 == 0:
              if new_false_set[iter] // 2 - 1 < i:
                  ans = -1
                  break
          else:
              if new_false_set[iter] // 2 < i:
                  ans = -1
                  break
  
          iter += 1
  
      print(ans)
  
  
  