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: /* package codechef; // don't place package name! */
   
  import java.util.*;
  import java.lang.*;
  import java.io.*;
   
  /* Name of the class has to be "Main" only if the class is public. */
  public class Codechef
  {
  	public static void main (String[] args) throws java.lang.Exception
  	{
  		// your code goes here
  		PrintWriter out = new PrintWriter(System.out);
          Scanner in = new Scanner(System.in);
  		
          int t=in.nextInt();
          while(t-- > 0){
           
           int n=in.nextInt();
           int[] arr=new int[n];
           boolean[] visit=new boolean[n+1];
           ArrayList<Integer> al1=new ArrayList<Integer>();
           ArrayList<Integer> al2=new ArrayList<Integer>();
           
           for(int i=0;i<n;i++){
               arr[i]=in.nextInt();
               if(arr[i]<=n) {
                   if(visit[arr[i]]) al1.add(arr[i]);
                   else visit[arr[i]]=true;
                   
               }
               else{
                   al1.add(arr[i]);
               }
           }
           
           for(int i=1;i<=n;i++){
               if(!visit[i]) al2.add(i);
           }
           
           Collections.sort(al1);
           Collections.sort(al2);
           
           boolean flag=false;
           for(int i=0;i<al1.size();i++){
               int k=al1.get(i);
               int m=al2.get(i);
               int l=k%(k-m);
               if(l!=m){
                   flag=true;
                   break;
               }
           }
           
           if(flag) out.println(-1);
           else out.println(al1.size());
           
          }
          out.flush();
  	}
  	
  	public static long GCD(long a, long b)
      {
        if (b == 0)
          return a;
        return GCD(b, a % b);
      }
      
  }
  