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.*;
  import java.io.*;
  import java.lang.*;
  public class codeforces {
     static int max=Integer.MAX_VALUE,min=Integer.MIN_VALUE;
      long maxl=Long.MAX_VALUE,minl=Long.MIN_VALUE;
      static PrintWriter pw = new PrintWriter(System.out);
      static StringBuilder sb=new StringBuilder();
      static int parent[] = new int[100001];
      static int mod = 1000000007;
      static boolean b1 = true;
  
      public static void main(String []args) {
          FastScanner sc = new FastScanner();
  
                int ttt = sc.nextInt();
  
                while (ttt-- > 0) {
                  int n = sc.nextInt();
  
                  int ar[] = new int[n+1];
                  for(int i=1;i<=n;i++)
                      ar[i] = sc.nextInt();
  
  
                  boolean b[] = new boolean[n+1];
                  ArrayList<Integer> al = new ArrayList<>();
  
                  for(int i=1;i<=n;i++){
                      if(ar[i]<=n&&!b[ar[i]]){
                          b[ar[i]] = true;
                      }
                      else
                          al.add(ar[i]);
                  }
                  Collections.sort(al);
                  b1 = true;
                  int j=0;
                  for(int i=1;i<=n;i++){
                      if(!b[i]){
                          if(!(2*i<al.get(j)))
                          {
                              b1=false;
                              break;
                          }
                          else
                              j++;
                      }
                  }
                  if(b1)
                      pw.println(j);
                  else
                      pw.println("-1");
  
                 pw.flush();
      }
  
  
      }
      public static Boolean[] primeNo() {
          Boolean[] is_prime = new Boolean[1000001];
          int max = 1000000;
          for (int i = 2; i <= max; i++)
              is_prime[i] = true;
          is_prime[0] = is_prime[1] = false;
          for (int i = 2; (long)i*i <= max; i++) {
              if (is_prime[i] == true) {
                  for (int j = (i*i); j <= max; j += i)
                      is_prime[j] = false;
              }
          }
          return is_prime;
      }
  
      public static void union(int a,int b){
          parent[a] += parent[b];
          parent[b] = a;
      }
      public static int find(int a){
          if(parent[a]<0)
              return a;
          return (parent[a] =find(parent[a]));
      }
  
      public static class Pair{
          public  int x;
          public  int y;
          public Pair(int x,int y){
              this.x=x;
              this.y=y;
          }
      }
      public static long gcd(long a,long b){
          if(a==0)
              return b;
          if(a>b){
              long k=b;
              b=a;
              a=k;
          }
          return gcd(b%a,a);
      }
      public static int binarySearch(long arr[],long x){
          int l=0,r=arr.length-1;
          int result1=-1;
          while(l<=r)
          {
              int mid = l+(r-l)/2;
              if(arr[mid]==x)
              {
                  return mid;
              }
              else if(arr[mid]>x) {
                  r = mid-1;
                  result1 = r;
              }
              else {
                  l = mid + 1;
  
              }
          }
          return result1;
      }
      public static class FastScanner {
          BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
          StringTokenizer st=new StringTokenizer("");
          String next() {
              while (!st.hasMoreTokens())
                  try {
                      st=new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              return st.nextToken();
          }
  
          int nextInt() {
              return Integer.parseInt(next());
          }
          int[] readArray(int n) {
              int[] a=new int[n];
              for (int i=0; i<n; i++) a[i]=nextInt();
              return a;
          }
          long nextLong() {
              return Long.parseLong(next());
          }
      }
  }