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: /*
                         _oo0oo_
                        o8888888o
                        88" . "88
                        (| -_- |)
                        0\  =  /0
                      ___/`---'\___
                    .' \\|     |// '.
                   / \\|||  :  |||// \
                  / _||||| -:- |||||- \
                 |   | \\\  -  /// |   |
                 | \_|  ''\---/''  |_/ |
                 \  .-\__  '-'  ___/-. /
               ___'. .'  /--.--\  `. .'___
            ."" '<  `.___\_<|>_/___.' >' "".
           | | :  `- \`.;`\ _ /`;.`/ - ` : | |
           \  \ `_.   \_ __\ /__ _/   .-` /  /
       =====`-.____`.___ \_____/___.-`___.-'=====
                         `=---='
   
  */
  
  import java.util.*;
  import java.math.*;
  import java.io.*;
  import java.lang.Math.*;
  
  public class KickStart2020 {
  	 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());
  		}
  
  		float nextFloat() {
  			return Float.parseFloat(next());
  		}
  
  		String nextLine() {
  			String str = "";
  			try {
  				str = br.readLine();
  			} catch (IOException e) {
  				e.printStackTrace();
  			}
  			return str;
  		}
  	}
  
  	static long gcd(long a, long b) {
  		if (b == 0)
  			return a;
  		return gcd(b, a % b);
  
  	}
  	static long lcm(long a, long b) {
  		return a / gcd(a, b) * b;
  	}
  
  	public static class Pair implements Comparable<Pair> {
  		public int index;
  		public String value;
  
  		public Pair(int index,String value) {
  			this.index = index;
  			this.value = value;
  		}
  
  		@Override
  		public int compareTo(Pair other) {
  			// multiplied to -1 as the author need descending sort order
  			if(other.index < this.index) return -1;
  			if(other.index > this.index) return 1;
  			return 0;
  		}
  		@Override
  		public String toString() {
  			return this.index + " " + this.value;
  		}
  	}
  	static boolean isPrime(long d) {
  		if (d == 3)
  			return false;
  		for (int i = 2; i <= (long) Math.sqrt(d); i++) {
  			if (d % i == 0)
  				return false;
  		}
  		return true;
  	}
  	static void decimalTob(int n, int k, Stack<Integer> ss) {
            int x = n % k;
            int y = n / k;
            ss.push(x);
            if(y > 0) {
          	   decimalTob(y, k, ss);
            }
  	}
  	static long powermod(long x, long y, long mod) {
  		long ans = 1;
  		x = x % mod;
  		if (x == 0)
  			return 0;
  		int i = 1;
  		while (y > 0) {
  			if ((y & 1) != 0)
  				ans = (ans * x) % mod;
  			y = y >> 1;
  			x = (x * x) % mod;
  		}
  		return ans;
  	}
  	static long power(long x, long y)
  	{
  	    long res = 1;
  	    while (y > 0)
  	    {
  	        if ((y & 1) != 0)
  	            res = res * x;	  
  	        y = y >> 1; 
  	        x = x * x;  
  	    }
  	    return res;
  	}
  	public static void main(String[] args) throws Exception {
  		FastReader sc = new FastReader();
  		PrintWriter out = new PrintWriter(System.out);
  		int t = sc.nextInt();
  		outerloop:
  			while(t-- > 0) {
                  int n = sc.nextInt();
                  TreeSet<Integer> ss = new TreeSet<>(Collections.reverseOrder());
                  TreeMap<Integer, Integer> ssd = new TreeMap<>();
                  int count = 0;
                  for(int i = 1; i <= n; i++) ss.add(i);
                  for(int i = 0; i < n; i++) {
                  	int a = sc.nextInt();
                  	if(ss.contains(a)) {
                  		ss.remove(a);
                  	}
                  	else {
                  		ssd.put((a + 1) / 2 - 1, ssd.getOrDefault((a + 1) / 2 - 1, 0) + 1);
                  		count++;
                  	}
                  }
                  for(int e: ss) {
                  	if(ssd.higherKey(e - 1) == null) {
                  		out.println(-1);
                  		continue outerloop;
                  	}
                  	else {
                  		Map.Entry<Integer, Integer> temp = ssd.higherEntry(e - 1);
                  		ssd.remove(temp.getKey());
                  		if(temp.getValue() - 1 >= 1)
                  		ssd.put(temp.getKey(), temp.getValue() - 1);
                  	}
                  }
                  out.println(count);
  			}
  		out.close();
  	}
  }