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.*;
  
  public class C {
      void go() {
          int n = Reader.nextInt();
          int[] arr = new int[n];
  
          TreeMap<Integer, Integer> map = new TreeMap<>();
  
          for(int i = 0; i < n; i++) {
              int x = Reader.nextInt();
              map.put(x, map.getOrDefault(x, 0) + 1);
          }
  
          //Arrays.sort(arr);
  
          int ans = 0;
          boolean[] found = new boolean[n + 1];
          for(int i = 1; i <= n; i++) {
              if(map.containsKey(i)) {
                  int f = map.get(i);
                  if(f == 1) map.remove(i);
                  else map.put(i, f - 1);
                  found[i] = true;
              }
          }
          for(int i = 1; i <= n; i++) {
              if(found[i]) continue;
              Integer c = map.ceilingKey(2 * i + 1);
              if(c == null) {
                  //Writer.println(i);
                  ans = -1;
                  break;
              }
              int f = map.get(c);
              if(f == 1) map.remove(c);
              else map.put(c, f - 1);
              ans++;
          }
  
          Writer.println(ans);
      }
      void solve() {
          for(int T = Reader.nextInt(); T > 0; T--) go();
      }
      void run() throws Exception {
          Reader.init(System.in);
          Writer.init(System.out);
          solve();
          Writer.close();
      }
  
      public static void main(String[] args) throws Exception {
          new C().run();
      }
  
      public static class Reader {
          public static StringTokenizer st;
          public static BufferedReader br;
  
          public static void init(InputStream in) {
              br = new BufferedReader(new InputStreamReader(in));
              st = new StringTokenizer("");
          }
  
          public static String next() {
              while(!st.hasMoreTokens()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      throw new InputMismatchException();
                  }
              }
              return st.nextToken();
          }
  
          public static int nextInt() {
              return Integer.parseInt(next());
          }
  
          public static long nextLong() {
              return Long.parseLong(next());
          }
  
          public static double nextDouble() {
              return Double.parseDouble(next());
          }
      }
  
      public static class Writer {
          public static PrintWriter pw;
  
          public static void init(OutputStream os) {
              pw = new PrintWriter(new BufferedOutputStream(os));
          }
  
          public static void print(String s) {
              pw.print(s);
          }
  
          public static void print(char c) {
              pw.print(c);
          }
  
          public static void print(int x) {
              pw.print(x);
          }
  
          public static void print(long x) {
              pw.print(x);
          }
  
          public static void println(String s) {
              pw.println(s);
          }
  
          public static void println(char c) {
              pw.println(c);
          }
  
          public static void println(int x) {
              pw.println(x);
          }
  
          public static void println(long x) {
              pw.println(x);
          }
  
          public static void close() {
              pw.close();
          }
      }
  }