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 java.util.*;
  
  //import javax.swing.plaf.basic.BasicInternalFrameTitlePane.SystemMenuBar;
  
  import java.lang.*;
  import java.io.*;
  
  public class Main
  {
   public static class FastReader {
  
  		BufferedReader b;
  		StringTokenizer s;
  		public FastReader() {
  			b=new BufferedReader(new InputStreamReader(System.in));
  		}
  		String next() {
  			while(s==null ||!s.hasMoreElements()) {
  				try {
  					s=new StringTokenizer(b.readLine());
  				}
  				catch(IOException e) {
  					e.printStackTrace();
  				}
  			}
  			return s.nextToken();
  		}
  		public int nextInt() {
  			return Integer.parseInt(next());
  		}
  		public long nextLong() {
  			return Long.parseLong(next());
  		}
  		public double nextDouble() {
  			return Double.parseDouble(next());
  		}
  		
  		String nextLine() {
  			String str="";
  			try {
  				str=b.readLine();
  			}
  			catch(IOException e) {
  				e.printStackTrace();
  			}
  			return str;
  		}
  		boolean hasNext() {
  		    if (s != null && s.hasMoreTokens()) {
  		        return true;
  		    }
  		    String tmp;
  		    try {
  		        b.mark(1000);
  		        tmp = b.readLine();
  		        if (tmp == null) {
  		            return false;
  		        }
  		        b.reset();
  		    } catch (IOException e) {
  		        return false;
  		    }
  		    return true;
  		}
  	
  }
   /*static int LEN = 10000000;
   int lp[]=new int[LEN+1];
   List<Inter>
   public void sieve()
   {
  	 for (int i=2; i <= N; ++i) {
  		    if (lp[i] == 0) {
  		        lp[i] = i;
  		        pr.push_back(i);
  		    }
  		    for (int j=0; j < (int)pr.size() && pr[j] <= lp[i] && i*pr[j] <= N; ++j) {
  		        lp[i * pr[j]] = pr[j];
  		    }
  		}
   }*/
   
   public static long gcd(long a,long b) {if(a==0)return b; return gcd(b%a,a);}
   public static int gcd(int a,int b) {if(a==0)return b; return gcd(b%a,a);};
   
   static int power(int x, int y){
       if (y == 0)
           return 1;
       else if (y % 2 == 0)
           return power(x, y / 2) * power(x, y / 2);
       else
           return x * power(x, y / 2) * power(x, y / 2);
   }
   
   static long power(long x , long y)
   {
  	 if (y == 0)
           return 1;
       else if (y % 2 == 0)
           return power(x, y / 2) * power(x, y / 2);
       else
           return x * power(x, y / 2) * power(x, y / 2);
   }
  
  	
  	public static void main (String[] args) throws java.lang.Exception
  	{
  		
  		
  		long mod=1000000007;
  		
  		FastReader in=new FastReader();
  		if(in.hasNext()){
  		  
  		if(in.hasNext()){
  		
  		BufferedWriter log = new BufferedWriter(new OutputStreamWriter(System.out));
  		
  		int test=in.nextInt();
  		
  		outer:while(test-->0)
  		{
  			int n=in.nextInt();
  			int arr[]=new int[n];
  			
  			for(int i=0;i<n;i++)
  				arr[i]=in.nextInt();
  			
  			Arrays.sort(arr);
  			
  			Set<Integer>set=new HashSet<>();
  			
  			int c=1;
  			
  			int ans=0;
  			for(int i=0;i<n;i++)
  			{
  				
  				
  				if(arr[i]<=n&&!set.contains(arr[i])) {
  					set.add(arr[i]);
  					continue;}
  				
  				while(set.contains(c))
  					c++;
  				
  				if(((arr[i]-1)/2)>0&&((arr[i]-1)/2)>=c) {
  					set.add(c);ans++;}
  				else {
  					
  					System.out.println(-1);
  					continue outer;
  				}
  			}
  			
  			System.out.println(ans);
  		}
  		
  		}
  }
  }
  }
  
  
  	
  
  
  	
  
  