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 codeforces;
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.*;
  public class solution{
  	public static void main(String[] args){
  		FastScanner s=new FastScanner();
      	PrintWriter out=new PrintWriter(System.out);
      	int t=s.nextInt();
      	for(int tt=0;tt<t;tt++) {
      		int n=s.nextInt();
      		int a[]=s.readArray(n);
      		int count[]=new int[n+1];
      		ArrayList<Integer> temp=new ArrayList<>(),temp2=new ArrayList<>();
      		for(int i=0;i<n;i++) {
      			if(a[i]<=n) {
      				count[a[i]]++;
      			}else {
      				temp2.add(a[i]);
      			}
      		}
      		for(int i=1;i<=n;i++) {
      			if(count[i]==0) {
      				temp.add(i);
      			}else {
      				for(int j=0;j<count[i]-1;j++) {
      					temp2.add(i);
      				}
      			}
      		}
      		
      		Collections.sort(temp);
      		Collections.sort(temp2);
      		long ans=temp.size();
      		for(int i=temp2.size()-1;i>=0;i--) {
      			if(temp.get(i)>=(temp2.get(i)+1)/2) {
      				ans=-1;
      				break;
      			}
      		}
      		out.println(ans);
      	}
      	out.close();
      }
  	public static void printb(boolean ans) {
  		if(ans) {
  			System.out.println("Yes");
  		}else {
  			System.out.println("No");
  		}
  	}
  	static boolean isPrime(int n){
          if (n <= 1)
              return false;
          else if (n == 2)
              return true;
          else if (n % 2 == 0)
              return false;
          for (int i = 3; i <= Math.sqrt(n); i += 2){
              if (n % i == 0)
                  return false;
          }
          return true;
      }
  	static long lcm(long a,long b){
  	      return (a*b)/(gcd(a,b));
  	    }
  	static long gcd(long a, long b){
  	      if (b == 0)
  	        return a;
  	      return gcd(b, a % b);
  	    }
      static void sort(long [] a) {
  		ArrayList<Long> l=new ArrayList<>();
  		for (long i:a) l.add(i);
  		Collections.sort(l);
  		for (int i=0; i<a.length; i++) a[i]=l.get(i);
  	}
      static void sort(int [] a) {
  		ArrayList<Integer> l=new ArrayList<>();
  		for (int i:a) l.add(i);
  		Collections.sort(l);
  		for (int i=0; i<a.length; i++) a[i]=l.get(i);
  	}
      static class FastScanner {
  		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
  		StringTokenizer st=new StringTokenizer("");
  		String next() {
  			while (!st.hasMoreTokens())
  				try {
  					st=new StringTokenizer(br.readLine());
  				} catch (IOException e) {
  					e.printStackTrace();
  				}
  			return st.nextToken();
  		}
  		double nextDouble() {
  			return Double.parseDouble(next());
  		}
  		int nextInt() {
  			return Integer.parseInt(next());
  		}
  		boolean nextBoolean() {
  			return Boolean.parseBoolean(next());
  		}
  		int[] readArray(int n) {
  			int[] a=new int[n];
  			for (int i=0; i<n; i++) a[i]=nextInt();
  			return a;
  		}
  		long nextLong() {
  			return Long.parseLong(next());
  		}
  		long[] readLongArray(int n) {
  			long[] a=new long[n];
  			for (int i=0; i<n; i++) a[i]=nextLong();
  			return a;
  		}
  	}
      static class Pair implements Comparable<Pair>{
      	int a,b; 
      	Pair(int a,int b){
      		this.a=a;
      		this.b=b;
      	}
      	public int compareTo(Pair o) {
      		if(b==o.b) {
      			return o.a-a;
      		}
      		return b-o.b;
      	}
      }
  }
  