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 Solution {
  	public static void main(String[] args) throws IOException {
  		try {
  			int t = sc.nextInt();
  			while (t-- > 0)
  				solve();
  		} catch (Exception e) {
  			return;
  		}
  	}
  
  	// SOLUTION STARTS HERE
  	// :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
  	static void solve() {
  		int n = sc.nextInt();
  		int a[] = sc.readIntArray(n);
  		TreeSet<Integer> set = new TreeSet<>();
  		for (int i = 1; i <= n; i++) {
  			set.add(i);
  		}
  		ArrayList<Integer> rem = new ArrayList<>();
  		for (int i : a) {
  			if (set.contains(i))
  				set.remove(i);
  			else
  				rem.add(i);
  		}
  		Collections.sort(rem);
  		for (int i : rem) {
  			int x = set.first();
  			if (i % (i - x) != x) {
  				System.out.println(-1);
  				return;
  			}
  			set.remove(x);
  		}
  		System.out.println(rem.size());
  	}
  	// SOLUTION ENDS HERE
  	// :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
  
  	static boolean[] seiveOfEratosthenes(int n) {
  		boolean[] isPrime = new boolean[n + 1];
  		Arrays.fill(isPrime, true);
  		for (int i = 2; i * i <= n; i++) {
  			for (int j = i * i; j <= n; j += i) {
  				isPrime[j] = false;
  			}
  		}
  		return isPrime;
  	}
  
  	static int gcd(int a, int b) {
  		if (b == 0)
  			return a;
  		return gcd(b, a % b);
  	}
  
  	static boolean isPrime(long n) {
  		if (n < 2)
  			return false;
  		for (int i = 2; i * i <= n; i++) {
  			if (n % i == 0)
  				return false;
  		}
  		return true;
  	}
  
  	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());
  		}
  
  		int[] readIntArray(int n) {
  			int a[] = new int[n];
  			for (int i = 0; i < n; i++) {
  				a[i] = Integer.parseInt(next());
  			}
  			return a;
  		}
  
  		void printIntArray(int a[]) {
  			for (int i = 0; i < a.length; i++) {
  				System.out.print(a[i] + " ");
  			}
  		}
  
  		long[] readLongArray(int n) {
  			long a[] = new long[n];
  			for (int i = 0; i < n; i++) {
  				a[i] = Long.parseLong(next());
  			}
  			return a;
  		}
  
  		void printLongArray(long a[]) {
  			for (int i = 0; i < a.length; i++) {
  				System.out.print(a[i] + " ");
  			}
  		}
  
  		double nextDouble() {
  			return Double.parseDouble(next());
  		}
  
  		String nextLine() {
  			String str = "";
  			try {
  				str = br.readLine();
  			} catch (IOException e) {
  				e.printStackTrace();
  			}
  			return str;
  		}
  	}
  
  	static class OutputWriter {
  		private final PrintWriter writer;
  
  		public OutputWriter(OutputStream outputStream) {
  			writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
  		}
  
  		public OutputWriter(Writer writer) {
  			this.writer = new PrintWriter(writer);
  		}
  
  		public void print(Object... objects) {
  			for (int i = 0; i < objects.length; i++) {
  				if (i != 0)
  					writer.print(' ');
  				writer.print(objects[i]);
  			}
  		}
  
  		public void println() {
  			writer.print("\n");
  		}
  
  		public void printLine(Object... objects) {
  			print(objects);
  			writer.println();
  		}
  
  		public void close() {
  			writer.close();
  		}
  
  		public void flush() {
  			writer.flush();
  		}
  
  	}
  
  	private static final FastReader sc = new FastReader();
  	private static final OutputWriter out = new OutputWriter(System.out);
  }
  