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 A {
      //--------------------------INPUT READER---------------------------------//
      static class fs {
          public BufferedReader br;
          StringTokenizer st = new StringTokenizer("");
  
          public fs() { this(System.in); }
          public fs(InputStream is) {
              br = new BufferedReader(new InputStreamReader(is));
          }
          String next() {
              while (!st.hasMoreTokens()) {
                  try { st = new StringTokenizer(br.readLine()); }
                  catch (IOException e) { e.printStackTrace(); }
              }
              return st.nextToken();
          }
  
          int ni() { return Integer.parseInt(next()); }
          long nl() { return Long.parseLong(next()); }
          double nd() { return Double.parseDouble(next()); }
          String ns() { return next(); }
  
          int[] na(long nn) {
              int n = (int) nn;
              int[] a = new int[n];
              for (int i = 0; i < n; i++) a[i] = ni();
              return a;
          }
  
          long[] nal(long nn) {
              int n = (int) nn;
              long[] l = new long[n];
              for(int i = 0; i < n; i++) l[i] = nl();
              return l;
          }
      }
      //-----------------------------------------------------------------------//
  
      //---------------------------PRINTER-------------------------------------//
      static class Printer {
          static PrintWriter w;
          public Printer() {this(System.out);}
          public Printer(OutputStream os) {
              w = new PrintWriter(os);
          }
          public void p(int i) {w.println(i);}
          public void p(long l) {w.println(l);}
          public void p(double d) {w.println(d);}
          public void p(String s) { w.println(s);}
          public void pr(int i) {w.print(i);}
          public void pr(long l) {w.print(l);}
          public void pr(double d) {w.print(d);}
          public void pr(String s) { w.print(s);}
          public void pl() {w.println();}
          public void close() {w.close();}
      }
      //-----------------------------------------------------------------------//
  
      //--------------------------VARIABLES------------------------------------//
      static fs sc = new fs();
      static OutputStream outputStream = System.out;
      static Printer w = new Printer(outputStream);
      static long lma = Long.MAX_VALUE, lmi = Long.MIN_VALUE;
      static long ima = Integer.MAX_VALUE, imi = Integer.MIN_VALUE;
      static long mod = 1000000007;
      //-----------------------------------------------------------------------//
  
      //--------------------------ADMIN_MODE-----------------------------------//
      private static void ADMIN_MODE() throws IOException {
          if (System.getProperty("ONLINE_JUDGE") == null) {
              w = new Printer(new FileOutputStream("output.txt"));
              sc = new fs(new FileInputStream("input.txt"));
          }
      }
      //-----------------------------------------------------------------------//
  
      //----------------------------START--------------------------------------//
      public static void main(String[] args)
              throws IOException {
  
          ADMIN_MODE();
  
          int t = sc.ni();while(t-->0)
              solve();
  
  
          w.close();
      }
  
      static void solve() throws IOException {
          int n = sc.ni();
          List<Long> li = new ArrayList<>();
          int[] hash = new int[n+1];
          for(int i = 1; i <= n; i++) {
              long curr = sc.nl();
              if(curr <= n && hash[(int)curr]!=1) {
                  hash[(int)curr]=1;
              } else li.add(curr);
          }
  
          Collections.sort(li);
  
          int ans = 0;
          int id = 0;
          for(int i = 1; i <= n; i++) {
              if(hash[i]==1) continue;
              else if(i < Math.ceil(li.get(id)/2.0)) {
                  ans++;
                  id++;
              } else {
                  w.p(-1);
                  return;
              }
          }
          w.p(ans);
      }
  
  }