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.*;
  
  public class Main {
      public static void main(String[] args) {
          Scanner sc=new Scanner(System.in);
          int T=sc.nextInt();
          while(T-->0) {
              int n=sc.nextInt();
              int ans=n;
              int[] array=new int[n+1];
              int[] arr=new int[n];
              int length=0;
              for(int i=0;i<n;i++) {
                  int input=sc.nextInt();
                  if(input<=n && array[input]==0) {
                      array[input]=1;
                      ans--;
                  }
                  else
                      arr[length++]=input-(input/2+1);
              }
              Arrays.sort(arr,0,length);
              boolean flag=true;
              int index=length-1;
              for(int i=n;i>0;i--) {
                  if(array[i]!=1) {
                      if(index<0) {
                          flag=false;
                          break;
                      }
                      if(arr[index]<i) {
                          flag=false;
                          break;
                      }
                      else
                          index--;
                  }
              }
              if(flag)
                  System.out.println(ans);
              else
                  System.out.println(-1);
          }
          sc.close();
      }
  }