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.*;
  import java.util.*;
  import java.math.*;
  import java.lang.*;
   
  import static java.lang.Math.*;
  
  public class Main implements Runnable {
      static class InputReader {
          private InputStream stream;
          private byte[] buf = new byte[1024];
          private int curChar;
          private int numChars;
          private SpaceCharFilter filter;
          private BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
   
          public InputReader(InputStream stream) {
              this.stream = stream;
          }
          
          public int read() {
              if (numChars==-1) 
                  throw new InputMismatchException();
              
              if (curChar >= numChars) {
                  curChar = 0;
                  try {
                      numChars = stream.read(buf);
                  }
                  catch (IOException e) {
                      throw new InputMismatchException();
                  }
                  
                  if(numChars <= 0)               
                      return -1;
              }
              return buf[curChar++];
          }
       
          public String nextLine() {
              String str = "";
              try {
                  str = br.readLine();
              }
              catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
          public int nextInt() {
              int c = read();
              
              while(isSpaceChar(c)) 
                  c = read();
              
              int sgn = 1;
              
              if (c == '-') {
                  sgn = -1;
                  c = read();
              }
              
              int res = 0;
              do {
                  if(c<'0'||c>'9') 
                      throw new InputMismatchException();
                  res *= 10;
                  res += c - '0';
                  c = read();
              }
              while (!isSpaceChar(c)); 
              
              return res * sgn;
          }
          
          public long nextLong() {
              int c = read();
              while (isSpaceChar(c))
                  c = read();
              int sgn = 1;
              if (c == '-') {
                  sgn = -1;
                  c = read();
              }
              long res = 0;
              
              do {
                  if (c < '0' || c > '9')
                      throw new InputMismatchException();
                  res *= 10;
                  res += c - '0';
                  c = read();
              }
              while (!isSpaceChar(c));
                  return res * sgn;
          }
          
          public double nextDouble() {
              int c = read();
              while (isSpaceChar(c))
                  c = read();
              int sgn = 1;
              if (c == '-') {
                  sgn = -1;
                  c = read();
              }
              double res = 0;
              while (!isSpaceChar(c) && c != '.') {
                  if (c == 'e' || c == 'E')
                      return res * Math.pow(10, nextInt());
                  if (c < '0' || c > '9')
                      throw new InputMismatchException();
                  res *= 10;
                  res += c - '0';
                  c = read();
              }
              if (c == '.') {
                  c = read();
                  double m = 1;
                  while (!isSpaceChar(c)) {
                      if (c == 'e' || c == 'E')
                          return res * Math.pow(10, nextInt());
                      if (c < '0' || c > '9')
                          throw new InputMismatchException();
                      m /= 10;
                      res += (c - '0') * m;
                      c = read();
                  }
              }
              return res * sgn;
          }
          
          public String readString() {
              int c = read();
              while (isSpaceChar(c))
                  c = read();
              StringBuilder res = new StringBuilder();
              do {
                  res.appendCodePoint(c);
                  c = read();
              } 
              while (!isSpaceChar(c));
              
              return res.toString();
          }
       
          public boolean isSpaceChar(int c) {
              if (filter != null)
                  return filter.isSpaceChar(c);
              return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
          }
       
          public String next() {
              return readString();
          }
          
          public interface SpaceCharFilter {
              public boolean isSpaceChar(int ch);
          }
      }
      public static void main(String args[]) throws Exception {
          new Thread(null, new Main(),"Main",1<<26).start();
      } 
      public int getColor(HashMap<Integer, Integer> map, int i) {
          if(map.containsKey(i))
              return map.get(i);
          return i;
      }
      int gcd(int a, int b) {
          if(b == 0)
              return a;
          return gcd(b, a % b);
      }
      void solve() {
          InputReader sc = new InputReader(System.in);
          PrintWriter out = new PrintWriter(System.out);
  
          int t = sc.nextInt();
          for(int x = 0; x < t; ++x) {
              int n = sc.nextInt();
              Integer a[] = new Integer[n];
              for(int i = 0; i < n; ++i)
                  a[i] = sc.nextInt();
  
              int reqEle[] = new int[n + 1];
  
              Arrays.sort(a);
  
              int cost = 0;
              int curEle = 1;
              for(int i = 1; i <= n; ++i) {
                  if(a[i - 1] <= n && reqEle[a[i - 1]] == 0) {
                      reqEle[a[i - 1]] = 1;
                      continue;
                  }
                  while(reqEle[curEle] == 1)
                      curEle++;
  
                  if(a[i - 1] < 2 * curEle + 1) {
                      cost = -1;
                      break;
                  }
                  reqEle[curEle] = 1;
                  curEle += 1;
                  cost++;
              }
  
              out.println(cost);
          }
          out.close();
      }
      public void run() {
          solve();
      }
      class Query {
          int type;
          int val1, val2;
          Query(int a, int b) {
              type = a;
              val1 = b;
          }
          Query(int a, int b, int c) {
              type = a;
              val1 = b;
              val2 = c;
          }
      }
  }