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.math.*;
  import java.util.* ;
  
  import java.io.* ;
  @SuppressWarnings("unused")
  //i am working for the day i will surpass you
  //Scanner in = new Scanner(new File("i.txt"));
  //in.close();
  //PrintWriter writer = new PrintWriter("o.txt");
  //writer.close();
   
  public class A
  {
  	static final int mod = (int)1e9+7 ;
  	static final double pi = 3.1415926536 ;
  	static boolean not_prime[] = new boolean[10000001] ;
  	static void sieve() {
  		for(int i=2 ; i*i<10000001 ; i++) {
  			if(not_prime[i]==false) {
  				for(int j=2*i ; j<10000001 ; j+=i) {
  					not_prime[j]=true ;
  				}
  			}
  		}not_prime[0]=true ; not_prime[1]=true ;
  	}		
  	public static long bexp(long base , long power)
  	{
  		long res=1L ;
  		
  		base = base%mod ;
  		
  		while(power>0) {
  			if((power&1)==1) {
  				res=(res*base)%mod ;
  				power-- ;
  			}
  			else {
  				base=(base*base)%mod ;
  				power>>=1 ;
  			}
  		}
  		
  		return res ;
  	}
  	static long modInverse(long n, long p){return power(n, p - 2, p); }
  	static long power(long x, long y, long p)
  	{
  	  
  	    // Initialize result
  	    long res = 1;
  	    x = x % p;
  	  
  	    while (y > 0) {
  	  
  	        if (y % 2 == 1)
  	            res = (res * x) % p;
  	        
  	        y = y >> 1;
  	        x = (x * x) % p;
  	    }
  	  
  	    return res;
  	}
  	static long nCrModPFermat(int n, int r, long p){if(n<r) return 0 ;if (r == 0)return 1; long[] fac = new long[n + 1];fac[0] = 1;for (int i = 1; i <= n; i++)fac[i] = fac[i - 1] * i % p;return (fac[n] * modInverse(fac[r], p) % p* modInverse(fac[n - r], p) % p) % p;}	
  	static long modular_add(long a, long b){ return ((a % mod) + (b % mod)) % mod; }
  	static long modular_sub(long a, long b){ return ((a % mod) - (b % mod) + mod) % mod; }
  	static long modular_mult(long a, long b){ return ((a % mod) * (b % mod)) % mod; }	
  	static long lcm(long f, long f2){ return (f / gcd(f, f2)) * f2; }
  	static long gcd(long a, long b){if (b == 0) {return a;}return gcd(b, a % b);}
  	static int cbits(long x) {return (int)(Math.log(x)/Math.log(2)+1) ;}
  	
  	public static void main(String[] args)throws Exception
      {
  		FastReader in = new FastReader() ;
  		StringBuilder op = new StringBuilder() ;
  		int T = in.nextInt(); 
  	//	int T=1 ;
  		for(int tt=0 ; tt<T ; tt++){
  			
  			int n = in.nextInt() ;
  			int a[] = in.readArray(n) ;
  			sort(a) ;
  			int check[] = new int[n+1] ;
  			List<Integer> greater = new ArrayList<>() ;
  			for(int el : a) {
  				if(el > n || check[el]==1)greater.add(el) ;
  				else check[el]=1 ;
  			}
  			List<Integer> req = new ArrayList<>() ;
  			for(int i=1 ; i<=n ; i++) {
  				if(check[i]==0)req.add(i) ;
  			}
  		//	System.out.println(req+" "+greater);
  			int f=0 , c=0 ;
  			for(int i=0 ; i<req.size() ; i++) {
  				int reqEl = req.get(i) ;
  				int gre = greater.get(i) ;
  				int range = ((gre&1)==1)?gre/2 : (gre-1)/2 ;
  				if(reqEl>range) {
  					f=1 ;
  					break ;
  				}
  				 c++ ;
  				 check[reqEl]=1 ;
  			}
  			if(f==0)op.append(c+"\n") ;
  			else op.append("-1\n") ;
  		}
  		System.out.println(op.toString());
      }
  	
  
  	static class pair implements Comparable<pair>
  	{
  		int first , second ;
  		pair(int first , int second){
  			this.first=first ;
  			this.second=second; 
  		}
  		public int compareTo(pair other) {
  			return this.second-other.second ;
  		}
  	}
  	
  	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 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[] readArray(int n) {
  			int[] a=new int[n];
  			for (int i=0; i<n; i++) a[i]=nextInt();
  			return a;
  		}
      }
  
  }