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: 
  def main():
          
      # if number is even, cannot reach [n // 2, n - 1]
      # if number is odd, cannot reach [n // 2 + 1, n - 1]
      
      t = int(input())
      allans = []
      for _ in range(t):
          n = int(input())
          a = readIntArr()
          
          takenIndexes = set()
          vi = [False] * (n + 1)
          for i, x in enumerate(a):
              if 1 <= x <= n and vi[x] == False:
                  vi[x] = True
                  takenIndexes.add(i)
          
          remainingItems = []
          for i in range(n):
              if i not in takenIndexes:
                  remainingItems.append(a[i])
          remainingItems.sort()
          
          requiredItems = []
          for x in range(1, n + 1):
              if vi[x] == False:
                  requiredItems.append(x)
          
          # map remainingItems to requiredItems Greedily in sequence
          m = len(remainingItems)
          possible = True
          for i in range(m):
              if requiredItems[i] * 2 >= remainingItems[i]:
                  possible = False
          if possible:
              allans.append(m)
          else:
              allans.append(-1)
          
      multiLineArrayPrint(allans)
      
      return
  
  
  
  import sys
  input=sys.stdin.buffer.readline #FOR READING PURE INTEGER INPUTS (space separation ok)
  # input=lambda: sys.stdin.readline().rstrip("\r\n") #FOR READING STRING/TEXT INPUTS.
  
  def oneLineArrayPrint(arr):
      print(' '.join([str(x) for x in arr]))
  def multiLineArrayPrint(arr):
      print('\n'.join([str(x) for x in arr]))
  def multiLineArrayOfArraysPrint(arr):
      print('\n'.join([' '.join([str(x) for x in y]) for y in arr]))
   
  def readIntArr():
      return [int(x) for x in input().split()]
  # def readFloatArr():
  #     return [float(x) for x in input().split()]
   
  def makeArr(defaultValFactory,dimensionArr): # eg. makeArr(lambda:0,[n,m])
      dv=defaultValFactory;da=dimensionArr
      if len(da)==1:return [dv() for _ in range(da[0])]
      else:return [makeArr(dv,da[1:]) for _ in range(da[0])]
   
  def queryInteractive(a, b, c):
      print('? {} {} {}'.format(a, b, c))
      sys.stdout.flush()
      return int(input())
   
  def answerInteractive(ansArr):
      print('! {}'.format(' '.join([str(x) for x in ansArr])))
      sys.stdout.flush()
   
  inf=float('inf')
  # MOD=10**9+7
  # MOD=998244353
  
  from math import gcd,floor,ceil
  import math
  # from math import floor,ceil # for Python2
   
  for _abc in range(1):
      main()