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.io.*;
  import java.util.*;
  
  public class tank {
  
      static final FastScanner fs = new FastScanner();
  
      static PrintWriter out = new PrintWriter(System.out);
  
      public static void main(String[] args) {
          int t = fs.nextInt();
          while(t-- > 0) run_case();
  
          out.close();
      }
  
      static void run_case() {
          int n = fs.nextInt();
          int[] a = fs.readArray(n);
  
          HashSet<Integer> hs = new HashSet<>();
          
          ArrayList<Integer> al = new ArrayList<>();
  
          for(int i: a) {
              if(i <= n && !hs.contains(i)) {
                  hs.add(i);
              } else {
                  al.add(i);
              }
          }
  
          Collections.sort(al);
  
          int j = al.size() - 1;
  
          int mov = 0;
  
          for (int i = n - 1; i >= 0; i--) {
              if(hs.contains(i + 1)) continue;
  
              if(al.get(j) % 2 == 0) {
                  if(i + 1 <= al.get(j) / 2 - 1) mov++;
                  else {
                      out.println(-1);
                      return;
                  }
              } else {
                  if(i + 1 <= al.get(j) / 2) mov++;
                  else {
                      out.println(-1);
                      return;
                  }
              }
  
              j--;
          }
  
          out.println(mov);
      }
  
      static void ruffleSort(int[] a) {
          int n=a.length;
          Random r=new Random();
          for (int i=0; i<a.length; i++) {
              int oi=r.nextInt(n), temp=a[i];
              a[i]=a[oi];
              a[oi]=temp;
          }
  
          Arrays.sort(a);
      }
  
      static class FastScanner {
          BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
          StringTokenizer st=new StringTokenizer("");
          String next() {
              while (!st.hasMoreTokens())
                  try {
                      st=new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              return st.nextToken();
          }
  
          String nextLine(){
              try {
                  return br.readLine();
              } catch (IOException e) {
                  e.printStackTrace();
              }
  
              return "";
          }
  
          int nextInt() {
              return Integer.parseInt(next());
          }
  
          int[] readArray(int n) {
              int[] a=new int[n];
              for (int i=0; i<n; i++) a[i]=nextInt();
              return a;
          }
  
          long nextLong() {
              return Long.parseLong(next());
          }
  
          double nextDouble() {
              return Double.parseDouble(next());
          }
      }
  }