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.IOException;
  import java.io.InputStreamReader;
  import java.util.*;
  public class C{
  	public static void main(String[] args){
  		FastReader sc = new FastReader();
  		int t=sc.nextInt();
  		next:while(t-->0){
  			int n=sc.nextInt();
  			boolean find[]=new boolean [n];
  			Map<Integer,Integer> map= new HashMap<Integer, Integer>();
  			for(int i=0;i<n;i++) {
  				int x=sc.nextInt();
  				if(map.containsKey(x))map.put(x, map.get(x)+1);
  				else map.put(x, 1);
  			}
  			ArrayList<Integer> ans = new ArrayList<Integer>();
  			for(Integer i:map.keySet()) {
  				if(i<=n)find[i-1]=true;
  				for(int j=0;j<map.get(i)-1;j++) ans.add(i);
  				if(i>n)ans.add(i);
  			}
  			Collections.sort(ans,Comparator.reverseOrder());
  			ArrayList<Integer>want= new ArrayList<Integer>();
  			for(int i=n-1;i>=0;i--)if(!find[i])want.add(i+1);
  			for(int i=0;i<ans.size();i++) {
  				if(ans.get(i)%(Math.abs(ans.get(i)-want.get(i)))!=want.get(i)) {
  					System.out.println(-1);
  					continue next;
  				}
  			}
  			System.out.println(ans.size());
  		}
      }
  	static void sort(int a[]) {
  		ArrayList<Integer> aa= new ArrayList<>();
  		for(int i:a)aa.add(i);
  		Collections.sort(aa);
  		int j=0;
  		for(int i:aa)a[j++]=i;
  	}
  	static class pair {
  		int x;int y;
  		 pair(int x,int y){
  			this.x=x;
  			this.y=y;
  		}
  		
  	}
  	static ArrayList<Integer> primeFac(int n){
  		ArrayList<Integer>ans = new ArrayList<Integer>();
  		int lp[]=new int [n+1];
  		Arrays.fill(lp, 0);  	//0-prime
  		for(int i=2;i<=n;i++) {
  			if(lp[i]==0) {
  				for(int j=i;j<=n;j+=i) {
  					if(lp[j]==0) lp[j]=i;
  				}
  			}
  		}
  		int fac=n;
  		while(fac>1) {
  			ans.add(lp[fac]);
  			fac=fac/lp[fac];
  		}
  		print(ans);
  		return ans;
  	}
  	static ArrayList<Long> prime_in_given_range(long l,long r){
  		ArrayList<Long> ans= new ArrayList<>();
  		int n=(int)Math.sqrt(r)+1;
  		int prime[]=sieve_of_Eratosthenes(n);
  		long res[]=new long [(int)(r-l)+1];
  		for(int i=0;i<=r-l;i++) {
  			res[i]=i+l;
  		}
  		for(int i=0;i<prime.length;i++) {
  			if(prime[i]==1) {
  				System.out.println(2);
  				for(int j=Math.max((int)i*i, (int)(l+i-1)/i*i);j<=r;j+=i) {
  					res[j-(int)l]=0; 
  				}
  			}
  		}
  		for(long i:res) if(i!=0)ans.add(i);
  		return ans;
  	}
  	static int [] sieve_of_Eratosthenes(int n) {
  		int prime[]=new int [n];
  		Arrays.fill(prime, 1);  // 1-prime | 0-not prime
  		prime[0]=prime[1]=0;
  		for(int i=2;i<n;i++) {
  			if(prime[i]==1) {
  				for(int j=i*i;j<n;j+=i) {
  					prime[j]=0;
  				}
  			}
  		}
  		return prime;
  	}
  	static long binpow(long a,long b) {
  		long res=1;
  		if(b==0)return a;
  		if(a==0)return 1;
  		while(b>0) {
  			if((b&1)==1) {
  				res*=a;
  			}
  			a*=a;
  			b>>=1;
  		}
  		return res;
  	}
  	static void print(int a[]) {
  		System.out.println(a.length);
  		for(int i:a) {
  			System.out.print(i+" ");
  		}
  		System.out.println();
  	}
  	static void print(long a[]) {
  		System.out.println(a.length);
  		for(long i:a) {
  			System.out.print(i+" ");
  		}
  		System.out.println();
  	}
  	static long rolling_hashcode(String s ,int st,int end,long Hashcode,int n) {
  		if(end>=s.length()) return -1;
  		int mod=1000000007;
  		
  		Hashcode=Hashcode-(s.charAt(st-1)*(long)Math.pow(27,n-1));
  		Hashcode*=10;
  		
  		Hashcode=(Hashcode+(long)s.charAt(end))%mod;
  		return Hashcode;
  		
  	}
  	static long  hashcode(String s,int n) {
  		long code=0;
  		for(int i=0;i<n;i++) {
  			code+=((long)s.charAt(i)*(long)Math.pow(27, n-i-1)%1000000007);
  		}
  		return code;
  	}
  	static void print(ArrayList<Integer> a) {
  		System.out.println(a.size());
  		for(long i:a) {
  			System.out.print(i+" ");
  		}
  		System.out.println();
  	}
  	static class FastReader {
  		BufferedReader br;
  		StringTokenizer st;
  
  		public FastReader()
  		{
  			br = new BufferedReader(
  				new InputStreamReader(System.in));
  		}
  		int [] fastArray(int n) {
  			int a[]=new int [n];
  			for(int i=0;i<n;i++) {
  				a[i]=nextInt();
  			}
  			return a;
  		}
  		String next()
  		{
  			while (st == null || !st.hasMoreElements()) {
  				try {
  					st = new StringTokenizer(br.readLine());
  				}
  				catch (IOException e) {
  					e.printStackTrace();
  				}
  			}
  			return st.nextToken();
  		}
  
  		int nextInt() { return Integer.parseInt(next()); }
  
  		long nextLong() { return Long.parseLong(next()); }
  
  		double nextDouble()
  		{
  			return Double.parseDouble(next());
  		}
  
  		String nextLine()
  		{
  			String str = "";
  			try {
  				str = br.readLine();
  			}
  			catch (IOException e) {
  				e.printStackTrace();
  			}
  			return str;
  		}
  	}
  
  }