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.awt.*;
  import java.awt.desktop.SystemEventListener;
  import java.io.*;
  import java.text.DecimalFormat;
  import java.util.*;
  import java.util.concurrent.locks.ReadWriteLock;
  
  
  public class Main {
  
      public static void main(String[] args) throws IOException {
          Reader.init(System.in);
          BufferedWriter output = new BufferedWriter(new OutputStreamWriter(System.out));
          int t = Reader.nextInt();
          while ( t > 0){
              int n = Reader.nextInt();
              int [] array = new int[n];
              int [] copy  = new int[n];
              int i = 0;
              while ( i < n){
                  array[i] = Reader.nextInt();
  
                  i++;
              }
              Arrays.sort(array);
              PriorityQueue<Integer> pq = new PriorityQueue<>();
              i = 0;
              while ( i < n){
                  if ( array[i] <= n){
                      if ( copy[array[i]-1] == 1){
                          pq.add(array[i]);
                      }
                      else{
                          copy[array[i]-1] = 1;
                      }
                  }else{
                      pq.add(array[i]);
                  }
                  i++;
              }
              i = 0;
              boolean ans = true;
              int count = 0;
              while ( i < n){
                  if (copy[i] == 0){
                      int v = pq.poll();
                      if ( sub(i+1,v) !=1){
                          ans =false;
                          break;
                      }
                      else{
                          count++;
                      }
                  }
                  i++;
              }
              if ( ans){
                  System.out.println(count);
              }
              else{
                  System.out.println(-1);
              }
  
  
  
  
              t--;
          }
          output.flush();
  
  
      }
      public static int sub(int a, int b){
         int half = b/2;
         if ( b%2 == 0){
             if ( a < half){
                 return 1;
             }
             else{
                 return -1;
             }
         }
         else{
             if ( a<= half){
                 return 1;
             }
             else{
                 return -1;
             }
         }
      }
  
  
      private static int bs(int low,int high,int[] array,int find){
          if ( low <= high ){
              int  mid = low + (high-low)/2;
              if ( array[mid] > find){
                  high = mid -1;
                  return bs(low,high,array,find);
              }
              else if ( array[mid] < find){
                  low = mid+1;
                  return bs(low,high,array,find);
              }
              return mid;
          }
          return -1;
      }
  
      private static int max(int a, int b) {
          return  Math.max(a,b);
      }
  
      private static int min(int a,int b){
          return  Math.min(a,b);
      }
  
      public static long modularExponentiation(long a,long b,long mod){
          if ( b == 1){
              return a;
          }
          else{
              long ans = modularExponentiation(a,b/2,mod)%mod;
              if ( b%2 == 1){
                  return (a*((ans*ans)%mod))%mod;
              }
  
              return ((ans*ans)%mod);
          }
      }
  
      public static long sum(long n){
          return  (n*(n+1))/2;
      }
      public static long abs(long a){
          return a < 0 ? (-1*a) : a;
      }
      public static long gcd(long a,long b){
          if ( a == 0){
              return b;
          }
          else{
              return gcd(b%a,a);
          }
      }
  
  
  }
  
  class Reader {
      static BufferedReader reader;
      static StringTokenizer tokenizer;
  
  
      static void init(InputStream input) {
          reader = new BufferedReader(
                  new InputStreamReader(input));
          tokenizer = new StringTokenizer("");
      }
  
      static String next() throws IOException {
          while ( ! tokenizer.hasMoreTokens() ) {
  
              tokenizer = new StringTokenizer(
                      reader.readLine() );
          }
          return tokenizer.nextToken();
      }
  
      static int nextInt() throws IOException {
          return Integer.parseInt( next() );
      }
  
      static double nextDouble() throws IOException {
          return Double.parseDouble( next() );
      }
  
      static long nextLong() throws IOException{
          return Long.parseLong(next());
      }
  }
  
  class NComparator implements Comparator<Node>{
      @Override
      public int compare(Node o1, Node o2) {
          if ( o2.position > o1.position){
              return 1;
          }
          else if ( o2.position < o1.position){
              return -1;
          }
          else{
              if ( o2.time < o1.time){
                  return 1;
              }
              else if ( o2.time > o2.time){
                  return -1;
              }
              else{
                  return 0;
              }
          }
      }
  }
  class DComparator implements Comparator<Integer>{
      @Override
      public int compare(Integer o1, Integer o2) {
          if ( o2 > o1){
              return 1;
          }
          else if ( o2 < o1){
              return -1;
          }
          else{
              return 0;
          }
      }
  }
  
  
  class Node{
      int position;
      long time;
  
      Node(int p,long t){
          position = p;
          time = t;
      }
  
  }