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 {
  
      private void solve() {
          int t = ri();
          while (t-- > 0) {
              int n = ri();
              int[] a = ria(n);
              a = sort(a);
              boolean flag = false;
              int count = 0;
              List<Integer> badInts = new ArrayList<>();
              boolean[] was = new boolean[n + 1];
              for (int i = 0; i < n; i++) {
                  if (a[i] <= n && !was[a[i]]) {
                      was[a[i]] = true;
                      continue;
                  }
  
                  badInts.add(a[i]);
                  count++;
              }
              Collections.sort(badInts);
              for (int i = 0, number = 1; i < badInts.size() && number < n + 1; number++) {
                  if (was[number] == true) continue;
                  if (badInts.get(i) % (badInts.get(i) - number) != number) {
                      flag = true;
                      break;
                  }
                  i++;
              }
  
              if (flag) {
                  out.println(-1);
              } else {
                  out.println(count);
              }
          }
      }
  
      //////////////////////////////////////////////////////////////////
  
      long sqrtLong(long x) {
          long root = (long) Math.sqrt(x);
          while (root * root > x) --root;
          while ((root + 1) * (root + 1) <= x) ++root;
          return root;
      }
  
      int gcd(int a, int b) {
          if (b == 0)
              return a;
          else
              return gcd(b, a % b);
      }
  
      int lcm(int a, int b) {
          return a / gcd(a, b) * b;
      }
  
      int phi(int n) {
          int result = n;
          for (int i = 2; i * i <= n; ++i)
              if (n % i == 0) {
                  while (n % i == 0)
                      n /= i;
                  result -= result / i;
              }
          if (n > 1)
              result -= result / n;
          return result;
      }
  
      int factmod(int n, int p) {
          int res = 1;
          while (n > 1) {
              res = (res * ((n / p) % 2 == 1 ? p - 1 : 1)) % p;
              for (int i = 2; i <= n % p; ++i)
                  res = (res * i) % p;
              n /= p;
          }
          return res % p;
      }
  
      int binpow(int a, int n) {
          int res = 1;
          while (n != 0) {
              if ((n & 1) != 0)
                  res *= a;
              a *= a;
              n >>= 1;
          }
          return res;
      }
  
      String solPyatnashki() {
          int a[] = new int[16];
          for (int i = 0; i < 16; ++i)
              a[i] = ri();
  
          int inv = 0;
          for (int i = 0; i < 16; ++i)
              if (a[i] != 0)
                  for (int j = 0; j < i; ++j)
                      if (a[j] > a[i])
                          ++inv;
          for (int i = 0; i < 16; ++i)
              if (a[i] == 0)
                  inv += 1 + i / 4;
  
  
          return ((inv & 1) != 0 ? "No Solution" : "Solution Exists");
      }
  
      boolean isPrime(int number) {
          for (int i = 2; i * i <= number; i++) {
              if (number % i == 0) {
                  return false;
              }
          }
          return number > 1;
      }
  
      boolean[] primes(int border) {
          boolean[] isPrimes = new boolean[border + 1];
          Arrays.fill(isPrimes, true);
          isPrimes[0] = false;
          isPrimes[1] = false;
          for (int i = 2; i < border + 1; i++) {
              if (!isPrimes[i]) continue;
              for (int k = i * 2; k < border; k += i) {
                  isPrimes[k] = false;
              }
          }
          return isPrimes;
      }
  
      int[] sort(int[] arr) {
          Integer[] a = new Integer[arr.length];
          for (int i = 0; i < arr.length; i++) {
              a[i] = arr[i];
          }
          Arrays.sort(a);
          for (int i = 0; i < a.length; i++) {
              arr[i] = a[i];
          }
          return arr;
      }
  
      long[] sort(long[] arr) {
          Long[] a = new Long[arr.length];
          for (int i = 0; i < arr.length; i++) {
              a[i] = arr[i];
          }
          Arrays.sort(a);
          for (int i = 0; i < a.length; i++) {
              arr[i] = a[i];
          }
          return arr;
      }
  
      int max(int[] a) {
          int max = Integer.MIN_VALUE;
          for (int i = 0; i < a.length; i++) {
              if (a[i] > max) max = a[i];
          }
          return max;
      }
  
      long fastMod(String s1, long n2) {
          long num = 0;
          for (int i = 0; i < s1.length() - 1; i++) {
              num += Integer.parseInt(String.valueOf(s1.charAt(i)));
              num *= 10;
              if (num >= n2) {
                  num = num % n2;
              }
          }
          return (num + Integer.parseInt(String.valueOf(s1.charAt(s1.length() - 1)))) % n2;
      }
  
      //////////////////////////////////////////////////////////////////
  
      private boolean yesNo(boolean yes) {
          return yesNo(yes, "YES", "NO");
      }
  
      private boolean yesNo(boolean yes, String yesString, String noString) {
          out.println(yes ? yesString : noString);
          return yes;
      }
  
      //////////////////////////////////////////////////////////////////
  
      private long rl() {
          return Long.parseLong(rs());
      }
  
      private double rd() {
          return Double.parseDouble(rs());
      }
  
      private int[] ria(int n) {
          int[] a = new int[n];
          for (int i = 0; i < n; ++i) a[i] = ri();
          return a;
      }
  
      private int ri() {
          return Integer.parseInt(rs());
      }
  
      private String rs() {
          while (!tok.hasMoreTokens()) {
              String nextLine = readLine();
              if (null == nextLine) return null;
              tok = new StringTokenizer(nextLine);
          }
  
          return tok.nextToken();
      }
  
      private String readLine() {
          try {
              return in.readLine();
          } catch (IOException e) {
              throw new RuntimeException(e);
          }
      }
  
      //////////////////////////////////////////////////////////////////
  
      private BufferedReader in;
      private StringTokenizer tok;
      private PrintWriter out;
  
      private void initFileIO(String inputFileName, String outputFileName) throws FileNotFoundException {
          in = new BufferedReader(new FileReader(inputFileName));
          out = new PrintWriter(outputFileName);
      }
  
      private void initConsoleIO() throws IOException {
          in = new BufferedReader(new InputStreamReader(System.in));
          out = new PrintWriter(System.out);
      }
  
      private void initIO() throws IOException {
          Locale.setDefault(Locale.US);
  
          String fileName = "";
  
          if (!fileName.isEmpty()) {
              initFileIO(fileName + ".in", fileName + ".out");
          } else {
              if (new File("input.txt").exists()) {
                  initFileIO("input.txt", "output.txt");
              } else {
                  initConsoleIO();
              }
          }
  
          tok = new StringTokenizer("");
      }
  
      //////////////////////////////////////////////////////////////////
  
      private void run() {
          try {
              long timeStart = System.currentTimeMillis();
  
              initIO();
              solve();
              out.close();
  
              long timeEnd = System.currentTimeMillis();
              System.err.println("Time(ms) = " + (timeEnd - timeStart));
          } catch (Exception e) {
              e.printStackTrace();
              throw new RuntimeException(e);
          }
      }
  
      public static void main(String[] args) {
          new C().run();
      }
  
      ///////////////////////////////////////////////////////////////////
  }
  