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 bisect import insort,bisect_right,bisect_left
  from sys import stdout, stdin, setrecursionlimit
  from heapq import heappush, heappop, heapify 
  from io import BytesIO, IOBase
  from collections import *
  from itertools import *
  from random import * 
  from string import *
  from queue import *
  from math import *
  from re import *
  from os import *
  
  ####################################---fast-input-output----#########################################
  
  
  class FastIO(IOBase):
      newlines = 0
  
      def __init__(self, file):
          self._fd = file.fileno()
          self.buffer = BytesIO()
          self.writable = "x" in file.mode or "r" not in file.mode
          self.write = self.buffer.write if self.writable else None
  
      def read(self):
          while True:
              b = read(self._fd, max(fstat(self._fd).st_size, 8192))
              if not b:
                  break
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
          self.newlines = 0
          return self.buffer.read()
  
      def readline(self):
          while self.newlines == 0:
              b = read(self._fd, max(fstat(self._fd).st_size, 8192))
              self.newlines = b.count(b"\n") + (not b)
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
          self.newlines -= 1
          return self.buffer.readline()
  
      def flush(self):
          if self.writable:
              write(self._fd, self.buffer.getvalue())
              self.buffer.truncate(0), self.buffer.seek(0)
  
  
  class IOWrapper(IOBase):
      def __init__(self, file):
          self.buffer = FastIO(file)
          self.flush = self.buffer.flush
          self.writable = self.buffer.writable
          self.write = lambda s: self.buffer.write(s.encode("ascii"))
          self.read = lambda: self.buffer.read().decode("ascii")
          self.readline = lambda: self.buffer.readline().decode("ascii")
  
  
  stdin, stdout = IOWrapper(stdin), IOWrapper(stdout)
  graph, mod, szzz =  {}, 10**9 + 7, lambda: sorted(zzz())
  def getStr(): return input()
  def getInt(): return int(input())
  def listStr(): return list(input())
  def getStrs(): return input().split()
  def isInt(s): return '0' <= s[0] <= '9'
  def input(): return stdin.readline().strip()
  def zzz(): return [int(i) for i in input().split()]
  def output(answer, end='\n'): stdout.write(str(answer) + end)
  def lcd(xnum1, xnum2): return (xnum1 * xnum2 // gcd(xnum1, xnum2))
  
  
  def getPrimes(N = 10**5):
      SN = int(sqrt(N))
      sieve = [i for i in range(N+1)]
      sieve[1] = 0
      for i in sieve:
          if i > SN:
              break
          if i == 0:
              continue
          for j in range(2*i, N+1, i):
              sieve[j] = 0
      prime = [i for i in range(N+1) if sieve[i] != 0] 
      return prime
  def primeFactor(n,prime=getPrimes()):
      lst = []
      mx=int(sqrt(n))+1
      for i in prime:
          if i>mx:break
          while n%i==0:
              lst.append(i)
              n//=i
      if n>1:
          lst.append(n)
      return lst    
  
  dx = [-1, 1, 0, 0, 1, -1, 1, -1]
  dy = [0, 0, 1, -1, 1, -1, -1, 1]
  daysInMounth = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
  
  
  #################################################---Some Rule For Me To Follow---#################################
  """
      --instants of Reading problem continuously try to understand them.
  
      --Try & again try, maybe you're just one statement away!
  
  """
  ##########################################b########---START-CODING---###############################################
  
  
  num = getInt()
  
  
  for _ in range(num):
      n = getInt()
      arr = szzz()
  
      cnt = [0]*(n+1)
      unused =[]
  
      for i in arr:
          if i<=n and cnt[i]:
              unused.append(i)
          elif i<=n:
              cnt[i]=1
          else:
              unused.append(i)
  
  
      ans = 0
  
      rem = []
  
      for i in range(1,n+1):
          if cnt[i]==0:
              rem.append(i)
      # print(unused)
      # print(rem)
      while unused:
          x = unused.pop()
          y = rem.pop()
          # print(x,y,'*')
          if (x-1)//2<y:
              ans=False
              break
          else:
              ans+=1
              cnt[y]=1
  
      res=True
  
      for i in range(1,n+1):
          if cnt[i]==0:
              res=False
   
      if res:
          print(ans)
      else:
          print(-1)
  
  
  
  
  
  
      
  
  
  
      
      
  
  
  
      
  
  
  
  
  
  
  
  
  
  
      
  
  
  
      
  
  
  
  
  