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: # Sujith
  from sys import stdin,stdout,setrecursionlimit
  from io import BytesIO, IOBase
  # from heapq import heappush as push,heappop as hp,heapify as h
  # from math import gcd,floor,sqrt,ceil
  from collections import Counter,deque as dq,defaultdict as dd
  # from itertools import accumulate as acc,permutations as perm
  # from bisect import bisect_left as bl,bisect_right as br,bisect as bis
   
  setrecursionlimit(10000)
   
  class FastIO(IOBase):
      newlines = 0
   
      def __init__(self, file):
          import os
          self.os = os
          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
          self.BUFSIZE = 8192
   
      def read(self):
          while True:
              a = self.os.read(self._fd, max(self.os.fstat(self._fd).st_size, self.BUFSIZE))
              if not a:
                  break
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(a), self.buffer.seek(ptr)
          self.newlines = 0
          return self.buffer.read()
   
      def readline(self):
          while self.newlines == 0:
              a = self.os.read(self._fd, max(self.os.fstat(self._fd).st_size, self.BUFSIZE))
              self.newlines = a.count(b"\n") + (not a)
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(a), self.buffer.seek(ptr)
          self.newlines -= 1
          return self.buffer.readline()
   
      def flush(self):
          if self.writable:
              self.os.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)
  input = lambda: stdin.readline().rstrip("\r\n")
   
  # inf = float('inf')
  # ninf = float('-inf')
  # abc = 'abcdefghijklmnopqrstuvwxyz'
  inp = lambda: int(input())
  st = lambda: input().strip()
  jn = lambda x,l: x.join(map(str,l))
  int_arr = lambda : list(map(int,input().strip().split()))
  str_arr = lambda :list(map(str,input().split()))
  get_str = lambda : map(str,input().strip().split())
  get_int = lambda: map(int,input().strip().split())
  get_float = lambda : map(float,input().strip().split())
   
  mod = 1000000007
   
  #main()
  for _ in range(inp()):
      n = inp()
      arr = int_arr()
   
      ans = []
      pres,miss = dd(int),[]
      for i in range(n):
          if arr[i] > n:
              if arr[i] % 2 != 0:
                  ans.append(arr[i] // 2)
              else:
                  ans.append((arr[i] // 2) - 1)
          else:
              if pres[arr[i]] == 1:
                  if arr[i] % 2 != 0:
                      ans.append(arr[i] // 2)
                  else:
                      ans.append((arr[i] // 2) - 1)
              else:
                  pres[arr[i]] = 1
      ind = 0
      tot = 0
      cond = True
      ans.sort()
      l = len(ans)
      for i in range(1,n + 1):
          if not pres[i]:
              if ind < l and ans[ind] >= i:
                  tot += 1
                  ind += 1
              else:
                  cond = False
                  break
      if not cond:
          print(-1)
      else:
          print(tot)
  