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: from sys import stdin, stdout
  rd = lambda: list(map(int, stdin.readline().split()))
  rds = lambda: stdin.readline().rstrip()
  ii = lambda: int(stdin.readline())
  INF = 1 << 62
  mod = 10**9 + 7
  
  for _ in range(ii()):
      n = ii()
      ar = rd()
      p = set(i for i in range(1, n+1))
  
      b = []
      for x in ar:
          if x in p:
              p.discard(x)
          else:
              b.append(x)
      
      limits = []
      for x in b:
          if x % 2 == 1:
              limits.append(x // 2)
          else:
              limits.append(x // 2 - 1)
      
      p = list(p)
      p.sort()
      limits.sort()
  
      res = len(p)
      for x,y in zip(p, limits):
          if y < x:
              res = -1
              break
  
      print(res)
  
  #stdout.write(' '.join(map(str, ar)))
  #stdout.write(f'{res}')
  
  