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.lang.*;
   import java.io.*;
  
  public class C_Paprika_and_Permutation
   {
       static int M = 1_000_000_007;
       static final PrintWriter out =new PrintWriter(System.out);
       static final FastReader fs = new FastReader();
       static boolean prime[];
       public static void main (String[] args) throws java.lang.Exception
       {
             
             int t= fs.nextInt();
           aaa:  for(int i=0;i<t;i++)
             {
                 int n= fs.nextInt();
                 int a[]=fs.arrayIn(n);
                 int gg[]=new int[n+1];
                 ArrayList<Integer> al = new ArrayList<>();
                 for(int j=0;j<n;j++){
                     if(a[j]<=n&&gg[a[j]]==0){
                         gg[a[j]]=1;
                     }else{
                         al.add(a[j]);
                     }
                 }
                 Collections.sort(al);
                 int ans=0;
                 int in=0;
                 for(int j=1;j<=n;j++){
                     if(gg[j]==0){
                         int req=j;
                         int op=al.get(in);
                         if((op-1)/2>=req){
                             in++;
                             gg[j]=1;
                             ans++;
                         }else{
                             out.println(-1);
                             continue aaa;
                         }
                     }
                 }
                 out.println(ans);
             }
             out.flush();
    }
    public static long power(long x, long y)
    {
        long temp;
        if (y == 0)
            return 1;
        temp = power(x, y / 2);
  
        if (y % 2 == 0)
            return modMult(temp,temp);
        else {
            if (y > 0)
                return modMult(x,modMult(temp,temp));
            else
                return (modMult(temp,temp)) / x;
        }
    }
    static void sieveOfEratosthenes(int n)
      {
           prime = new boolean[n + 1];
          for (int i = 0; i <= n; i++)
              prime[i] = true;
              prime[0]=false;
              if(1<=n)
              prime[1]=false;
          for (int p = 2; p * p <= n; p++)
          {
              
              if (prime[p] == true)
              {
                 
                  for (int i = p * p; i <= n; i += p)
                      prime[i] = false;
              }
          }
      }
           static class FastReader 
           {
           BufferedReader br;
           StringTokenizer st;
    
           public FastReader()
           {
               br = new BufferedReader(
                   new InputStreamReader(System.in));
           }
    
           String next()
           {
               while (st == null || !st.hasMoreElements()) {
                   try {
                       st = new StringTokenizer(br.readLine());
                       }
                   catch (IOException e) {
                       e.printStackTrace();
                       }
           }
               return st.nextToken();
           }
    
           int nextInt() { return Integer.parseInt(next()); }
    
           long nextLong() { return Long.parseLong(next()); }
    
           double nextDouble()
           {
               return Double.parseDouble(next());
           }
    
           String nextLine()
           {
               String str = "";
               try {
                   str = br.readLine();
               }
               catch (IOException e) {
                   e.printStackTrace();
               }
               return str;
           }
   int [] arrayIn(int n) throws IOException
       {
           int  arr[] = new int[n];
           for(int i=0; i<n; i++)
           {
               arr[i] = nextInt();
           }
           return arr;
       }
       }
       
       public static class Pairs implements Comparable<Pairs>
       {
           int value,index;
           Pairs(int value, int index)
           {
               this.value = value;
               this.index = index;
           }
           public int compareTo(Pairs p)
           {
               return Integer.compare(this.value, p.value);
           }
       }
       static final Random random = new Random();
    
       static void ruffleSort(int arr[])
       {
           int n = arr.length;
           for(int i=0; i<n; i++)
           {
               int j = random.nextInt(n),temp = arr[j];
               arr[j] = arr[i];
               arr[i] = temp;
           }
           Arrays.sort(arr);
       }
       static long nCk(int n, int k) {
           return (modMult(fact(n),fastexp(modMult(fact(n-k),fact(k)),M-2)));
       }
    
       static long fact (long n) {
    
           long fact =1;
           for(int i=1; i<=n; i++) {
               fact = modMult(fact,i);
           }
           return fact%M;
       }
    
       static long modMult(long a,long b) {
           return a*b%M;
       }
    
       static long fastexp(long x, int y){
           if(y==1) return x;
    
           long ans = fastexp(x,y/2);
           if(y%2 == 0) return modMult(ans,ans);
           else return modMult(ans,modMult(ans,x));
       }
   }