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 Main
  {
      static class FastReader {
          BufferedReader br;
          StringTokenizer st;
   
          public FastReader()
          {
              br = new BufferedReader(
                  new InputStreamReader(System.in));
          }
   
          String next()
          {
              while (st == null || !st.hasMoreElements()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  }
                  catch (IOException e) {
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
   
          int nextInt() { return Integer.parseInt(next()); }
   
          long nextLong() { return Long.parseLong(next()); }
   
          double nextDouble()
          {
              return Double.parseDouble(next());
          }
   
          String nextLine()
          {
              String str = "";
              try {
                  str = br.readLine();
              }
              catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
      }
      static long modPow(long var, long num) {
      long m = 1;
      while (num > 0) {
          m = (m * var) %1000000007;
          --num;
      }
      return m;}
  	public static void main (String[] args) throws java.lang.Exception
  	{
  		FastReader s = new FastReader();
  		 BufferedWriter output = new BufferedWriter(
              new OutputStreamWriter(System.out));
  		int t=s.nextInt();
  		for(int w=0;w<t;w++)
  		{
  		    int n=s.nextInt();
  		   
  		    int[] arr= new int[n];
  		    
  		    for(int i=0;i<n;i++)
  		    {
  		        arr[i]=s.nextInt();
  		        
  		    }
  		    int flag=0;
  		    int ans=0;
  		    Arrays.sort(arr);
  		    int[] arr2= new int[n+1];
  		    int[] lim= new int[n+1];
  		    for(int i=0;i<n;i++)
  		    {
  		        if(arr[i]<=n)
  		        {
  		            if(arr2[arr[i]]>0)
  		            {
  		               ans++;
  		                arr2[arr[i]]--;
  		                if(Math.max(arr[i]%((arr[i]+1)/2),arr[i]%((arr[i]+1)/2+1))<n)
  		                 lim[Math.max(arr[i]%((arr[i]+1)/2),arr[i]%((arr[i]+1)/2+1))]++;
  		                else
  		                 lim[n]++;
  		            }
  		            arr2[arr[i]]++;
  		            
  		        }
  		        else
  		        {    if(Math.max(arr[i]%((arr[i]+1)/2),arr[i]%((arr[i]+1)/2+1))<n)
  		                 lim[Math.max(arr[i]%((arr[i]+1)/2),arr[i]%((arr[i]+1)/2+1))]++;
  		                else
  		                 lim[n]++;
  		            ans++;
  		        }
  		        
  		    }
  		     for(int i=n-1;i>-1;i--)
  		     {
  		         lim[i]=lim[i]+lim[i+1];
  		     }
  		     int k=0;
  		      for(int i=n;i>0;i--)
  		      {
  		          if(arr2[i]==0)
  		          {
  		              //output.write(String.valueOf(lim[i]-k)+"\n");
  		              if(lim[i]-k>0)
  		              {
  		                  lim[i]--;
  		                  k++;
  		              }
  		              else
  		              {
  		                  flag=1;
  		                  break;
  		              }
  		          }
  		      }
  		      if(flag==1)
  		      {
  		          output.write("-1\n");
  		      }
  		     else
  		         output.write(String.valueOf(ans)+"\n");
  		
  		}
  		output.flush();
  	}
  }
  