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: import array
  import bisect
  import heapq
  import math
  import collections
  import sys
  import copy
  from functools import reduce
  import decimal
  from io import BytesIO, IOBase
  import os
  import itertools
  import functools
  from types import GeneratorType
  
  #
  # sys.setrecursionlimit(10 ** 9)
  decimal.getcontext().rounding = decimal.ROUND_HALF_UP
  
  graphDict = collections.defaultdict
  
  queue = collections.deque
  
  
  ################## pypy deep recursion handling ##############
  # Author = @pajenegod
  def bootstrap(f, stack=[]):
      def wrappedfunc(*args, **kwargs):
          to = f(*args, **kwargs)
          if stack:
              return to
          else:
              while True:
                  if type(to) is GeneratorType:
                      stack.append(to)
                      to = next(to)
                  else:
                      stack.pop()
                      if not stack:
                          return to
                      to = stack[-1].send(to)
  
      return wrappedfunc
  
  
  ################## Graphs ###################
  class Graphs:
      def __init__(self):
          self.graph = graphDict(set)
  
      def add_edge(self, u, v):
          self.graph[u].add(v)
          self.graph[v].add(u)
  
      def dfs_utility(self, nodes, visited_nodes, colors, parity, level):
          global count
          if nodes == 1:
              colors[nodes] = -1
          else:
              if len(self.graph[nodes]) == 1 and parity % 2 == 0:
                  if q == 1:
                      colors[nodes] = 1
                  else:
                      colors[nodes] = -1
                      count += 1
              else:
                  if parity % 2 == 0:
                      colors[nodes] = -1
                  else:
                      colors[nodes] = 1
          visited_nodes.add(nodes)
          for neighbour in self.graph[nodes]:
              new_level = level + 1
              if neighbour not in visited_nodes:
                  self.dfs_utility(neighbour, visited_nodes, colors, level - 1, new_level)
  
      def dfs(self, node):
          Visited = set()
          color = collections.defaultdict()
          self.dfs_utility(node, Visited, color, 0, 0)
          return color
  
      def bfs(self, node, f_node):
          count = float("inf")
          visited = set()
          level = 0
          if node not in visited:
              queue.append([node, level])
              visited.add(node)
          flag = 0
          while queue:
              parent = queue.popleft()
              if parent[0] == f_node:
                  flag = 1
                  count = min(count, parent[1])
              level = parent[1] + 1
              for item in self.graph[parent[0]]:
                  if item not in visited:
                      queue.append([item, level])
                      visited.add(item)
          return count if flag else -1
          return False
  
  
  ################### Tree Implementaion ##############
  class Tree:
      def __init__(self, data):
          self.data = data
          self.left = None
          self.right = None
  
  
  def inorder(node, lis):
      if node:
          inorder(node.left, lis)
          lis.append(node.data)
          inorder(node.right, lis)
      return lis
  
  
  def leaf_node_sum(root):
      if root is None:
          return 0
      if root.left is None and root.right is None:
          return root.data
      return leaf_node_sum(root.left) + leaf_node_sum(root.right)
  
  
  def hight(root):
      if root is None:
          return -1
      if root.left is None and root.right is None:
          return 0
      return max(hight(root.left), hight(root.right)) + 1
  
  
  ################## Union Find #######################
  class UnionFind():
      parents = []
      sizes = []
      count = 0
  
      def __init__(self, n):
          self.count = n
          self.parents = [i for i in range(n)]
          self.sizes = [1 for i in range(n)]
  
      def find(self, i):
          if self.parents[i] == i:
              return i
          else:
              self.parents[i] = self.find(self.parents[i])
              return self.parents[i]
  
      def unite(self, i, j):
          root_i = self.find(i)
          root_j = self.find(j)
          if root_i == root_j:
              return
          elif root_i < root_j:
              self.parents[root_j] = root_i
              self.sizes[root_i] += self.sizes[root_j]
          else:
              self.parents[root_i] = root_j
              self.sizes[root_j] += self.sizes[root_i]
  
      def same(self, i, j):
          return self.find(i) == self.find(j)
  
      def size(self, i):
          return self.sizes[self.find(i)]
  
      def group_count(self):
          return len(set(self.find(i) for i in range(self.count)))
  
      def answer(self, extra, p, q):
          dic = collections.Counter()
          for q in range(n):
              dic[self.find(q)] = self.size(q)
          hq = list(dic.values())
          heapq._heapify_max(hq)
          ans = -1
          for z in range(extra + 1):
              if hq:
                  ans += heapq._heappop_max(hq)
              else:
                  break
          return ans
  
  
  #################################################
  
  def rounding(n):
      return int(decimal.Decimal(f'{n}').to_integral_value())
  
  
  def factors(n):
      return set(reduce(list.__add__,
                        ([i, n // i] for i in range(1, int(n ** 0.5) + 1) if (n % i == 0 and n // i > 3))))
  
  
  def p_sum(array):
      return list(itertools.accumulate(array))
  
  
  def base_change(nn, bb):
      if nn == 0:
          return [0]
      digits = []
      while nn:
          digits.append(int(nn % bb))
          nn //= bb
      return digits[::-1]
  
  
  def diophantine(a: int, b: int, c: int):
      d, x, y = extended_gcd(a, b)
      r = c // d
      return r * x, r * y
  
  
  @bootstrap
  def extended_gcd(a: int, b: int):
      if b == 0:
          d, x, y = a, 1, 0
      else:
          (d, p, q) = yield extended_gcd(b, a % b)
          x = q
          y = p - q * (a // b)
  
      yield d, x, y
  
  
  ######################################################################################
  
  '''
  Knowledge and awareness are vague, and perhaps better called illusions.
  Everyone lives within their own subjective interpretation.
                                                              ~Uchiha Itachi
  '''
  
  ################################ <fast I/O> ###########################################
  BUFSIZE = 8192
  
  
  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 = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
              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, **kwargs):
          while self.newlines == 0:
              b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
              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:
              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")
  
  
  sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
  
  
  #############################################<I/O Region >##############################################
  
  
  def inp():
      return sys.stdin.readline().strip()
  
  
  def map_inp(v_type):
      return map(v_type, inp().split())
  
  
  def list_inp(v_type):
      return list(map_inp(v_type))
  
  
  ######################################## Solution ####################################
  
  
  for _ in range(int(inp())):
      n = int(inp())
      arr = list_inp(int)
      arr.sort()
      visited = set()
      start = 1
      count = 0
      for item in arr:
          if 1 <= item <= n and item not in visited:
              visited.add(item)
              continue
          while start in visited:
              start += 1
          if start <= (item-1) // 2:
              count += 1
              visited.add(start)
      if len(visited) == n:
          print(count)
      else:
          print(-1)
  