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.ArrayList;
  import java.util.Collections;
  import java.util.Scanner;
  
  import static java.lang.Math.max;
  
  public class Main {
  
      public static int solution(int n, ArrayList<Integer> t) {
          int ans = 0;
          Collections.sort(t);
  //        for (int i = 0; i < n; i++) {
  //            if (t.get(i) == i + 1)
  //                continue;
  //
  //            int a = t.get(i), b = i + 1, c = a - b;
  //            if (c <= b)
  //                return -1;
  //            ans++;
  //        }
  
          int k = 0;
          int j = 0;
          ArrayList<Integer> used = new ArrayList();
          int next_unused = 0;
          for (int i = 0; i < n; i++)
              used.add(0);
          for (int i = 0; i < n; i++) {
              int b = i + 1;
              while(k < n && t.get(k) < b)
                  k++;
              while(j < n && (t.get(j) < 2 * b + 1 || used.get(j) == 1))
                  j++;
  
              next_unused = max(next_unused, k);
              while(next_unused < n && used.get(next_unused) == 1) {
                  next_unused++;
                  continue;
              }
              while(next_unused >= n && k < n && t.get(k) <= b)
                  k++;
  
              //System.err.println("" + b + " " + t.get(k) + " " + t.get(j));
              if (k < n && t.get(k) == b) {
                  if (used.get(k) == 1 && next_unused < n) {
                      used.set(next_unused, 1);
                      next_unused++;
                      continue;
                  }
  
                  used.set(k, 1);
                  k++;
                  continue;
              }
              if (j < n && t.get(j) >= 2 * b + 1) {
                  used.set(j, 1);
                  j++;
                  ans++;
                  continue;
              }
              return -1;
          }
  
          return ans;
      }
  
      public static void main(String[] args) {
  	// write your code here
          Scanner in = new Scanner(System.in);
          int Q = in.nextInt();
          in.nextLine();
          for (int q = 0; q < Q; q++) {
              int n = in.nextInt();
              ArrayList<Integer> t = new ArrayList();
              for (int i = 0 ; i < n; i++) {
                  int a = in.nextInt();
                  t.add(a);
              }
              System.out.println(solution(n, t));
          }
      }
  }
  