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.BufferedReader;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.FileOutputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.math.BigInteger;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.BitSet;
  import java.util.Calendar;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.LinkedList;
  import java.util.PriorityQueue;
  import java.util.SortedSet;
  import java.util.Stack;
  import java.util.StringTokenizer;
  import java.util.TreeMap;
  import java.util.TreeSet;
  
  /**
   * #
   *
   * @author pttrung
   */
  public class C_Round_761_Div2 {
      public static int MOD = 998244353;
  
      static double[][][] dp;
  
  
      public static void main(String[] args) throws FileNotFoundException {
          // PrintWriter out = new PrintWriter(new FileOutputStream(new File(
          // "output.txt")));
          PrintWriter out = new PrintWriter(System.out);
          Scanner in = new Scanner();
          int T = in.nextInt();
          for (int z = 0; z < T; z++) {
  
              int n = in.nextInt();
              int[] data = new int[n];
  
              for (int i = 0; i < n; i++) {
                  data[i] = in.nextInt();
              }
              int result = 0;
              boolean[] check = new boolean[n + 1];
              PriorityQueue<Integer> list = new PriorityQueue<>();
              for (int i = 0; i < n; i++) {
                  if (data[i] < check.length && !check[data[i]]) {
                      check[data[i]] = true;
                      continue;
                  }
                  list.add(data[i]);
              }
              LinkedList<Integer> need = new LinkedList<>();
              for (int i = 1; i < check.length; i++) {
                  if (!check[i]) {
                      need.add(i);
                  }
              }
              while (!list.isEmpty()) {
                  int i = list.poll();
                  int tmp = need.pollFirst();
                  if (tmp * 2 < i) {
                      result++;
                  } else {
                      result = -1;
                      break;
                  }
  
              }
              out.println(result);
  
          }
  
          out.close();
      }
  
  
      static int abs(int a) {
          return a < 0 ? -a : a;
      }
  
  
      public static int[] KMP(String val) {
          int i = 0;
          int j = -1;
          int[] result = new int[val.length() + 1];
          result[0] = -1;
          while (i < val.length()) {
              while (j >= 0 && val.charAt(j) != val.charAt(i)) {
                  j = result[j];
              }
              j++;
              i++;
              result[i] = j;
          }
          return result;
  
      }
  
      public static boolean nextPer(int[] data) {
          int i = data.length - 1;
          while (i > 0 && data[i] < data[i - 1]) {
              i--;
          }
          if (i == 0) {
              return false;
          }
          int j = data.length - 1;
          while (data[j] < data[i - 1]) {
              j--;
          }
          int temp = data[i - 1];
          data[i - 1] = data[j];
          data[j] = temp;
          Arrays.sort(data, i, data.length);
          return true;
      }
  
      public static int digit(long n) {
          int result = 0;
          while (n > 0) {
              n /= 10;
              result++;
          }
          return result;
      }
  
      public static double dist(long a, long b, long x, long y) {
          double val = (b - a) * (b - a) + (x - y) * (x - y);
          val = Math.sqrt(val);
          double other = x * x + a * a;
          other = Math.sqrt(other);
          return val + other;
  
      }
  
      public static class Point {
  
          int x;
          int y;
  
          public Point(int start, int end) {
              this.x = start;
              this.y = end;
          }
  
          public String toString() {
              return x + " " + y;
          }
  
      }
  
      public static class FT {
  
          long[] data;
  
          FT(int n) {
              data = new long[n];
          }
  
          public void update(int index, long value) {
              while (index < data.length) {
                  data[index] += value;
                  index += (index & (-index));
              }
          }
  
          public long get(int index) {
  
              long result = 0;
              while (index > 0) {
                  result += data[index];
                  index -= (index & (-index));
              }
              return result;
  
          }
      }
  
      public static long gcd(long a, long b) {
          if (b == 0) {
              return a;
          }
          return gcd(b, a % b);
      }
  
      public static long pow(long a, int b) {
          if (b == 0) {
              return 1;
          }
          if (b == 1) {
              return a;
          }
  
          long val = pow(a, b / 2);
          if (b % 2 == 0) {
              return (val * val);
          } else {
              return (val * ((val * a)));
  
          }
      }
  
      static class Scanner {
  
          BufferedReader br;
          StringTokenizer st;
  
          public Scanner() throws FileNotFoundException {
              // System.setOut(new PrintStream(new BufferedOutputStream(System.out), true));
              br = new BufferedReader(new InputStreamReader(System.in));
              //br = new BufferedReader(new InputStreamReader(new FileInputStream(new File("input.txt"))));
          }
  
          public String next() {
  
              while (st == null || !st.hasMoreTokens()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (Exception e) {
                      throw new RuntimeException();
                  }
              }
              return st.nextToken();
          }
  
          public long nextLong() {
              return Long.parseLong(next());
          }
  
          public int nextInt() {
              return Integer.parseInt(next());
          }
  
          public double nextDouble() {
              return Double.parseDouble(next());
          }
  
          public String nextLine() {
              st = null;
              try {
                  return br.readLine();
              } catch (Exception e) {
                  throw new RuntimeException();
              }
          }
  
          public boolean endLine() {
              try {
                  String next = br.readLine();
                  while (next != null && next.trim().isEmpty()) {
                      next = br.readLine();
                  }
                  if (next == null) {
                      return true;
                  }
                  st = new StringTokenizer(next);
                  return st.hasMoreTokens();
              } catch (Exception e) {
                  throw new RuntimeException();
              }
          }
      }
  }
  