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 Main {
      public static long mod = 1000000007;
      public static long mod2 = 998244353;
      static int N = 100050;
      static int[] lpf = new int[N];
      static int[] mobius = new int[N];
  
      public static void main(String[] args) throws java.lang.Exception {
          Reader sc = new Reader();
          FastNum in = new FastNum(System.in);
          PrintWriter out = new PrintWriter(System.out);
          BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  
          int tests = in.nextInt();
          for (int test = 1; test <= tests; test++) {
              int n = in.nextInt();
              int[] a = new int[n];
              int[] c = new int[n+1];
              boolean[] b = new boolean[n+1];
              for (int i = 0; i < n; i++) {
                  a[i] = in.nextInt();
              }
              for(int i : a) {
                  if(i <= n) {
                      if(b[i]) {
                          if(i % 2 == 0) {
                              c[i/2 - 1]++;
                          }
                          else c[i / 2]++;
                      } else b[i] = true;
                  }
                  else {
                      int temp = (i % 2 == 0) ? i / 2 - 1 : i / 2;
                      if(temp <= n) c[temp]++;
                      else c[n]++;
                  }
              }
              boolean f = true;
              int t = 0;
              int ans = 0;
              for(int i = n; i >= 1; i--) {
                  if(!b[i]) {
                      t += c[i];
                      if(t <= 0) {
                          f = false;
                          break;
                      } else {
                          t--;
                          ans++;
                      }
                  } else t += c[i];
              }
              if(f) out.println(ans);
              else out.println("-1");
          }
  
  
          out.flush();
      }
  
  
  
      public static int gcd(int a, int b) {
          if (a == 0)
              return b;
          return gcd(b % a, a);
      }
  
      public static long power(long a, long b) {
          if (b == 0)
              return 1;
          long answer = power(a, b / 2) % mod;
          answer = (answer * answer) % mod;
          if (b % 2 != 0)
              answer = (answer * a) % mod;
          return answer;
      }
  
      public static void swap(int x, int y) {
          int t = x;
          x = y;
          y = t;
      }
  
      public static long min(long a, long b) {
          if (a < b) return a;
          return b;
      }
  
      public static long divide(long a, long b) {
          return (a % mod * (power(b, mod - 2) % mod)) % mod;
      }
  
      public static long nCr(long n, long r) {
          long answer = 1;
          long k = min(r, n - r);
          for (long i = 0; i < k; i++) {
              answer = (answer % mod * (n - i) % mod) % mod;
              answer = divide(answer, i + 1);
          }
          return answer % mod;
      }
  
      public static boolean plaindrome(String str) {
          StringBuilder sb = new StringBuilder();
          sb.append(str);
          return (str.equals((sb.reverse()).toString()));
      }
  
      public static class Pair {
          int a;
          int b;
  
          Pair(int s, int e) {
              a = s;
              b = e;
          }
      }
  
      static class Assert {
          static void check(boolean e) {
              if (!e) {
                  throw new AssertionError();
              }
          }
      }
  
      static class FastNum implements AutoCloseable {
  
          InputStream is;
          byte buffer[] = new byte[1 << 16];
          int size = 0;
          int pos = 0;
  
          FastNum(InputStream is) {
              this.is = is;
          }
  
          int nextChar() {
              if (pos >= size) {
                  try {
                      size = is.read(buffer);
                  } catch (IOException e) {
                      throw new IOError(e);
                  }
                  pos = 0;
                  if (size == -1) {
                      return -1;
                  }
              }
              Assert.check(pos < size);
              int c = buffer[pos] & 0xFF;
              pos++;
              return c;
          }
  
          int nextInt() {
              int c = nextChar();
              while (c == ' ' || c == '\r' || c == '\n' || c == '\t') {
                  c = nextChar();
              }
              if (c == '-') {
                  c = nextChar();
                  Assert.check('0' <= c && c <= '9');
                  int n = -(c - '0');
                  c = nextChar();
                  while ('0' <= c && c <= '9') {
                      int d = c - '0';
                      c = nextChar();
                      Assert.check(n > Integer.MIN_VALUE / 10
                              || n == Integer.MIN_VALUE / 10 && d <= -(Integer.MIN_VALUE % 10));
                      n = n * 10 - d;
                  }
                  return n;
              } else {
                  Assert.check('0' <= c && c <= '9');
                  int n = c - '0';
                  c = nextChar();
                  while ('0' <= c && c <= '9') {
                      int d = c - '0';
                      c = nextChar();
                      Assert.check(
                              n < Integer.MAX_VALUE / 10 || n == Integer.MAX_VALUE / 10 && d <= Integer.MAX_VALUE % 10);
                      n = n * 10 + d;
                  }
                  return n;
              }
          }
  
          @Override
          public void close() {
          }
      }
  
  
      static class Reader {
          final private int BUFFER_SIZE = 1 << 16;
          private final DataInputStream din;
          private final byte[] buffer;
          private int bufferPointer, bytesRead;
  
          public Reader() {
              din = new DataInputStream(System.in);
              buffer = new byte[BUFFER_SIZE];
              bufferPointer = bytesRead = 0;
          }
  
          public Reader(String file_name) throws IOException {
              din = new DataInputStream(new FileInputStream(file_name));
              buffer = new byte[BUFFER_SIZE];
              bufferPointer = bytesRead = 0;
          }
  
          public String readLine() throws IOException {
              byte[] buf = new byte[64]; // line length
              int cnt = 0, c;
              while ((c = read()) != -1) {
                  if (c == '\n')
                      break;
                  buf[cnt++] = (byte) c;
              }
              return new String(buf, 0, cnt);
          }
  
          public int nextInt() throws IOException {
              int ret = 0;
              byte c = read();
              while (c <= ' ')
                  c = read();
              boolean neg = (c == '-');
              if (neg)
                  c = read();
              do {
                  ret = ret * 10 + c - '0';
              } while ((c = read()) >= '0' && c <= '9');
  
              if (neg)
                  return -ret;
              return ret;
          }
  
          public long nextLong() throws IOException {
              long ret = 0;
              byte c = read();
              while (c <= ' ')
                  c = read();
              boolean neg = (c == '-');
              if (neg)
                  c = read();
              do {
                  ret = ret * 10 + c - '0';
              }
              while ((c = read()) >= '0' && c <= '9');
              if (neg)
                  return -ret;
              return ret;
          }
  
          public double nextDouble() throws IOException {
              double ret = 0, div = 1;
              byte c = read();
              while (c <= ' ')
                  c = read();
              boolean neg = (c == '-');
              if (neg)
                  c = read();
  
              do {
                  ret = ret * 10 + c - '0';
              }
              while ((c = read()) >= '0' && c <= '9');
  
              if (c == '.') {
                  while ((c = read()) >= '0' && c <= '9') {
                      ret += (c - '0') / (div *= 10);
                  }
              }
  
              if (neg)
                  return -ret;
              return ret;
          }
  
          private void fillBuffer() throws IOException {
              bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
              if (bytesRead == -1)
                  buffer[0] = -1;
          }
  
          private byte read() throws IOException {
              if (bufferPointer == bytesRead)
                  fillBuffer();
              return buffer[bufferPointer++];
          }
  
          public void close() throws IOException {
              if (din == null)
                  return;
              din.close();
          }
      }
  }
  