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.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.StringTokenizer;
  
  // Paprika and Permutation
  public class PaprikaAndPermutation {
  
      public static void main(String[] args) throws IOException {
          PaprikaAndPermutation.solution();
      }
  
      private static void solution() throws IOException {
          PrintWriter printWriter = new PrintWriter(System.out);
          MyScanner scanner = new MyScanner();
          int numCases = scanner.nextInt();
          for (int i = 0; i < numCases; i++) {
              int n = scanner.nextInt();
              List<Integer> arr = new ArrayList<>();
              for (int j = 0; j < n; j++) {
                  arr.add(scanner.nextInt());
              }
              Collections.sort(arr);
              boolean[] seen = new boolean[n + 1];
              int x = 1;
              int ans = 0;
              for (int j = 0; j < n; j++) {
                  if (arr.get(j) >= 1 && arr.get(j) <= n && !seen[arr.get(j)]) {
                      seen[arr.get(j)] = true;
                  } else {
                      if (x * 2 >= arr.get(j)) {
                          break;
                      } else {
                          seen[x] = true;
                          ans++;
                      }
                  }
                  while (x < seen.length && seen[x]) {
                      x++;
                  }
              }
              if (x == n + 1) {
                  printWriter.println(ans);
              } else {
                  printWriter.println("-1");
              }
          }
          printWriter.close();
      }
  
      public static class MyScanner {
          private BufferedReader bufferedReader;
          private StringTokenizer st;
  
          public MyScanner() {
              bufferedReader = new BufferedReader(new InputStreamReader(System.in));
          }
  
          public String next() throws IOException {
              while (st == null || !st.hasMoreTokens()) {
                  st = new StringTokenizer(bufferedReader.readLine());
              }
              return st.nextToken();
          }
  
          public int nextInt() throws IOException {
              return Integer.parseInt(next());
          }
      }
  }
  