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 C {
      public static void main(String[] args) {
          for (int i = 0; i < N; i++) {
              solve();
          }
          out.close();
      }
  
      public static void solve() {
          int M = sc.nextInt();
          int[] a = new int[M];
          boolean[] b = new boolean[M];
          int index = 0;
          for (int i = 0; i < M; i++) {
              a[i] = sc.nextInt();
          }
          Arrays.sort(a);
          int res = 0;
          for (int i = 0; i < M; i++) {
              if (a[i] <= M && !b[a[i] - 1]) {
                  b[a[i] - 1] = true;
              } else if (((a[i] & 1) == 0 ? a[i] / 2 - 1 : a[i] / 2) >= index + 1) {
                  b[index] = true;
                  res++;
              } else {
                  out.println(-1);
                  return;
              }
              while (index < M && b[index]) {
                  index++;
              }
          }
          out.println(res);
      }
  
      private static PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));
  
      private static MyScanner sc = new MyScanner();
  
      private static int N = sc.nextInt();
  
      private static class MyScanner {
          BufferedReader br;
          StringTokenizer st;
  
          public MyScanner() {
              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());
          }
  
          String nextLine() {
              String str = "";
              try {
                  str = br.readLine();
              } catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
      }
  
      private static String build(List list) {
          if (list == null) {
              return "";
          } else {
              StringBuilder sb = new StringBuilder();
              for (Object o : list) {
                  sb.append(o.toString());
                  sb.append(" ");
              }
              return sb.toString();
          }
      }
  }