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 java.io.*;
  
  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; 
          }
          int[] nextIntArray(int n)
          {
              int arr[]=new int[n];
              for(int i=0;i<n;i++)
              {
                  arr[i]=Integer.parseInt(next());
              }
              return arr;
          }
          Integer[] nextIntegerArray(int n)
          {
              Integer arr[]=new Integer[n];
              for(Integer i=0;i<n;i++)
              {
                  arr[i]=Integer.parseInt(next());
              }
              return arr;
          }
          long[] nextLongArray(int n)
          {
              long arr[]=new long[n];
              for(int i=0;i<n;i++)
              {
                  arr[i]=Long.parseLong(next());
              }
              return arr;
          }
      } 
  	
  	/*
  	If we keep on subtracting the larger number from a smaller number gcd doesn't change. Hence, when smaller==larger (or) smaller divides larger we have our gcd=smaller.
  	*/
  	static long gcd(long larger,long smaller){
  		if(larger%smaller==0){
  			return smaller;
  		}
  		return gcd(smaller,larger%smaller);
  	}
  	
  	/*static long modularInverse(long a,long mod){
  	    long ans=1;
  	    long y=mod-2;
  	    while(y>0){
  	        if((y&1)==1){
  	            ans=((ans%mod)*(a%mod))%mod;
  	        }
  	        y>>=1;
  	        a=((a%mod)*(a%mod))%mod;
  	    }
  	    return ans%mod;
  	}
  	
  	static long nCr(int n,int r){//Uses fermat's little theorem for calculating modular inverse of r! and (n-r)!
  	    if(r>n){
  	        return 0;
  	    }
  	    if(r==0 || r==n){
  	        return 1;
  	    }
  	    if(n-r<r){
  	        r=n-r;
  	    }
  	    long mod=1000000000+7;
  	    long ans=1;
  	    long product=1;
  	    long in1=1;
  	    long in2=1;
  	    for(int i=1;i<=n;i++){
  	        product=((product%mod)*(i%mod))%mod;
  	        if(i==r){
  	            in1=modularInverse(product,mod);
  	        }
  	        if(i==n-r){
  	            in2=modularInverse(product,mod);
  	        }
  	    }
  	    return ((((product%mod)*(in1%mod))%mod)*(in2%mod));
  	}*/
  	
  	
  	/*static void swap(char [] s,int i,int j){
  		char t=s[i];
  		s[i]=s[j];
  		s[j]=t;
  	}
  	
  	static void permute(char[] s,int l,int r,int n){
  		
  		if(l<r){
  			for(int i=l;i<=r;i++){
  				swap(s,l,i);
  				permute(s,l+1,r,n);
  				swap(s,l,i);
  			}
  		}
  		else{
  			System.out.println(new String(s));
  		}
  		
  	}*/
  	
  	static long power(long a,long b){
  	    int mod=1000000007;
  	    long ans=1;
  	    while(b>0){
  	        if(b%2==1){
  	            ans=(ans*a)%mod;
  	        }
  	        b/=2;
  	        a=(a*a)%mod;
  	    }
  	    return ans;
  	}
  	
  	static int min(int a,int b){
  	    return (int)Math.min(a,b);
  	}
  	
  	static int max(int a,int b){
  	    return (int)Math.max(a,b);
  	}
  	
  	static int abs(int a,int b) {
  		return (int)Math.abs(a-b);
  	}
  	
      public static void main(String args[]) throws UnsupportedEncodingException, IOException {
          FastReader sc=new FastReader();
  		BufferedWriter out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(java.io.FileDescriptor.out), "ASCII"), 512);
  		//Below is the code to be used when dealing file handling for input and output.
  		/*BufferedReader br = new BufferedReader(
                                 new FileReader("input.txt"));
  		PrintWriter pw=new PrintWriter(new
                  BufferedWriter(new FileWriter("output.txt")));
  		pw.flush();
  		pw.close();*/
  		int te=sc.nextInt();
  		for(int qu=0;qu<te;qu++){
  			int n=sc.nextInt(),count=0;
  			int[] arr=sc.nextIntArray(n);
  			int[] set=new int[n+1];
  			ArrayList<Integer> list=new ArrayList<>();
  			for(int i=0;i<n;i++) {
  				if(arr[i]<=n && set[arr[i]]==0) {
  					set[arr[i]]=1;
  				}
  				else {
  					list.add(arr[i]);
  				}
  			}
  			Collections.sort(list);
  			int j=0;
  			for(int i=1;i<=n;i++) {
  				if(set[i]==1) continue;
  				if(list.get(j)<=2*i) {
  					count=-1;
  					break;
  				}
  				count++;
  				j++;
  				set[i]=1;
  			}
  			out.write(count+"\n");
  			out.flush();
  		}
  		out.close();
      }
  }
  