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.lang.Math;
  import java.io.* ;
  
  
  public class Account {
  	
  	public static class Pair<Object1 ,Object2> {
  	    Object1 key ;
  	    Object2 val ;
  	    
  	    Pair(Object1 key ,Object2 val) {
  	        this.key = key ;
  	        this.val = val ;
  	    }
  	    
  	    Pair() {}
  	    
  	}
  	
  	public static void main (String[] args) {
  		
  //		Scanner sc = new Scanner(System.in) ;
  		FastReader sc = new FastReader() ;
  //		StringBuilder res = new StringBuilder() ;
  		int t= 1 ;  
  		t = sc.nextInt() ;
  		while(t-- > 0) {
  			int n= sc.nextInt() ;
  			long sml= 1 ;
  			Set<Long> set = new HashSet<>() ;
  			List<Long> list = new ArrayList<>() ;
  			List<Long> rem = new ArrayList<>() ;
  			long[] arr = new long[n] ;
  			for(int i=0 ;i<n ;i++) {
  				arr[i] = sc.nextLong() ;
  			}
  			Arrays.sort(arr);
  			for(int i=0 ;i<n ;i++) {
  				if(i > 0  &&  arr[i] == arr[i-1]) {
  					list.add(arr[i]) ;
  				}else if(arr[i] <=n  &&  arr[i] > 0  &&  set.contains(arr[i]) == false) {
  					set.add(arr[i]) ;
  				}else {
  					list.add(arr[i]) ;
  				}
  			}for(long i=1 ;i<=n ;i++) {
  				if(set.contains(i) == false) {
  					rem.add(i) ;
  				}
  			}
  			boolean flag = true ;
  			int in = rem.size()-1 ,ans = rem.size() ;
  //			System.out.println(rem+" "+list);
  			for(int i=list.size()-1 ;i>=0 ;i--) {
  				long x = rem.get(in) ;
  				in-- ;
  				if(x*2 >= list.get(i)) {
  					flag = false ;
  					break ;
  				}
  			}if(flag) {
  				System.out.println(ans);
  			}else {
  				System.out.println("-1");
  			}
    		}
  	}
  	
  	
  	/*
  	 *   1--> a   3b   2c
  	 *   2--> 2a  b    3c
  	 *   3--> 3a  2b   c
  	 */
  		
  	
  	public static long gcd(long a, long b)
  	{
  	    if (b == 0)
  	        return a;
  	    return gcd(b, a % b);
  	     
  	}
  	
  	
  //	_xor from 1 to n
  	public static int xor(int n)
      {
          if (n % 4 == 0)
              return n;
        
          if (n % 4 == 1)
              return 1;
        
          if (n % 4 == 2)
              return n + 1;
        
          return 0;
      }
  
  	
  	public 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 [] readintarray(int n) {
              int res [] = new int [n];
              for(int i = 0; i<n; i++)res[i] = nextInt();
              return res;
          }
          long [] readlongarray(int n) {
              long res [] = new long [n];
              for(int i = 0; i<n; i++)res[i] = nextLong();
              return res;
          }
      }	
  	
  }