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 sys
  import math as mt
  import collections as cc
  input = sys.stdin.readline
  I = lambda : list(map(int,input().split()))
  mod = 10**9+7
  def ch(temp):
  	tans = 0
  	for i in range(len(temp)-k-1,-1,-k):
  		tans += 2*abs(temp[i])
  	return tans 
  
  for tc in range(int(input())):
  	n, =I()
  	ar = I()
  	ar.sort()
  	visi = cc.defaultdict(int)
  	temp = []
  	x = []
  	c = cc.Counter(ar)
  
  	for i in range(1,n+1):
  		if c[i]:
  			visi[i] = 1
  			continue
  		else:
  			x.append(i)
  	#print(visi)
  	#print(x)
  	xx = []
  	for i in ar:
  		if visi[i]:
  			visi[i] = 0
  			continue
  		xx.append(i)
  	#print(xx)
  	tf = 1
  	for i in range(len(x)):
  		req = x[i]
  		hand = (xx[i]-1)//2
  		if hand>=req:
  			continue
  		tf = 0
  	if tf:
  		print(len(x))
  	else:
  		print(-1)
  
  	# for i in range(n):
  	# 	if ar[i]==i+1:
  	# 		visi[i+1] = 1
  	# 		continue
  	# 	else:
  	# 		x.append(i+1)
  	# 		req = i+1
  	# 		hand = (ar[i]-1)//2
  	# 		temp.append((req,hand))
  	# temp.sort()
  	# print(temp)
  	# tf = 1
  	# ans = 0
  	# for j in range(len(temp)):
  	# 	if temp[j][1]>=(x[j]):
  	# 		ans+=1
  	# 		continue
  	# 	tf = 0
  	# if tf:
  	# 	print(ans)
  	# else:
  	# 	print(-1)
  
  