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: // Problem: C. Paprika and Permutation
  // Contest: Codeforces - Codeforces Round #761 (Div. 2)
  // URL: https://codeforces.com/contest/1617/problem/C
  // Memory Limit: 256 MB
  // Time Limit: 1000 ms
  
  import java.io.*;
  import java.util.*;
  
  import static java.lang.Math.max;
  import static java.lang.Math.min;
  import static java.lang.Math.abs;
  
  
  
  public class X1631 {
      long mod = 1000000007;
      private void preparation() {
  
      }
  
  
      private void clear() {
  
      }
  
      private void solve() throws Exception {
          rf();
          int n = ri();
          rf();int [] d = readArr(n);
          boolean [] f = new boolean[n + 1];
          ArrayList<Integer> a = new ArrayList<>();
          for(int i : d){
              if(i <= n && !f[i]){
                  f[i] = true;
              }else{
                  a.add(i);
              }
          }
          Collections.sort(a);
          int idx = 0;
          for(int i = 1; i <= n; i++){
              if(!f[i]){
                  if((a.get(idx) - 1) / 2 < i){
                      addAns(-1);
                      return ;
                  }
                  idx++;
              }
          }
          addAns(a.size());
  		
      }
  
      private void run() throws Exception {
  		
          int T = 1;
  		rf();
  		T = ri();
  		
  		preparation();
          while (T-- > 0) {
              solve();
              if (T != 0) {
                  clear();
              }
          }
          printAns();
      }
  
      public static void main(String[] args) throws Exception {
          new X1631().run();
      }
  
      StringBuilder sb = new StringBuilder();
      BufferedReader infile = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer strT;
  
  	private void addAns(int a){
  		sb.append(a + "\n");
  	}
  	
  	private void addAns(long a){
  		sb.append(a + "\n");
  	}
  	
  	private void addAns(String s){
  		sb.append(s + "\n");
  	}
  
      private void rf() throws IOException {
          strT = new StringTokenizer(infile.readLine());
      }
  
  
      private int ri() {
          return Integer.parseInt(strT.nextToken());
      }
  
      private long rl() {
          return Long.parseLong(strT.nextToken());
      }
  
  	private char [] rs2c(){
  		return strT.nextToken().toCharArray();
  	}
  	
  	private String rs(){
  		return strT.nextToken();
  	}
  
      private void printAns() {
          System.out.println(sb);
      }
  
      private int[] readArr(int N) throws Exception {
          int[] arr = new int[N];
          for (int i = 0; i < N; i++) {
              arr[i] = Integer.parseInt(strT.nextToken());
          }
          return arr;
      }
  
  	private long[] readArr2(int N) throws Exception {
          long[] arr = new long[N];
          for (int i = 0; i < N; i++) {
              arr[i] = Long.parseLong(strT.nextToken());
          }
          return arr;
      }
  
  	private void print(String format, Object ... args){
  		System.out.println(String.format(format,args));
  	}
  	
  	// for interactive problem. flush output after print.
  	private void iprint(String format, Object ... args){
  		System.out.println(String.format(format,args));
  		System.out.flush();
  	}
  
      private void print(int[] arr, int x) {
          //for debugging only
          for (int i = 0;i < min(arr.length, x); i++) {
              System.out.print(arr[i] + " ");
          }
          System.out.println();
      }
      
      private void print(long[] arr, int x) {
          //for debugging only
          for (int i = 0;i < min(arr.length, x); i++) {
              System.out.print(arr[i] + " ");
          }
          System.out.println();
      }
  
      
  }
  