You are given a sequence of integers of length n and integer number k. You should print any integer number x in the range of [1; 10^9] (i.e. 1 ≤ x ≤ 10^9) such that exactly k elements of given sequence are less than or equal to x.

Note that the sequence can contain equal elements.

If there is no such x, print "-1" (without quotes).

Input

The first line of the input contains integer numbers n and k (1 ≤ n ≤ 2 ⋅ 10^5, 0 ≤ k ≤ n). The second line of the input contains n integer numbers a_1, a_2, ..., a_n (1 ≤ a_i ≤ 10^9) — the sequence itself.

Output

Print any integer number x from range [1; 10^9] such that exactly k elements of given sequence is less or equal to x.

If there is no such x, print "-1" (without quotes).

Examples

Input

7 4
3 7 5 1 10 3 20


Output

6

Input

7 2
3 7 5 1 10 3 20


Output

-1

Note

In the first example 5 is also a valid answer because the elements with indices [1, 3, 4, 6] is less than or equal to 5 and obviously less than or equal to 6.

In the second example you cannot choose any number that only 2 elements of the given sequence will be less than or equal to this number because 3 elements of the given sequence will be also less than or equal to this number.
import java.io.*;
import java.util.*;
import javafx.util.Pair;
import javax.swing.*;
 



public class Codeforces {

 
 static PrintWriter pw=new PrintWriter(System.out);
 
 
    public static void main(String[] args) throws IOException {
      Reader.init(System.in);
     
     int n=Reader.nextInt();
     int k=Reader.nextInt();
     ArrayList <Integer>ar=new ArrayList();
    
     
       
     
     
        for (int i = 0; i <n; i++) 
            ar.add(Reader.nextInt());
        
      Collections.sort(ar);
      
        
        
        if(k==0&&ar.get(0)==1){
            pw.println(-1);
            pw.close();
            return ;
        
        
        }
        
        
        
        else if(k==0&&ar.get(0)!=1)
        { pw.println(1);
            pw.close();
            return;}
        else   if(n==k)
        {pw.println(ar.get(k-1));pw.close();return;}
        
        else{
           
        if(ar.get(k).equals(ar.get(k-1)))
            pw.println(-1);
        else pw.println(ar.get(k-1));
        }
     
       
        
        
        pw.close();
      }}
 
 
class Reader {
 
        static BufferedReader reader;
        static StringTokenizer tokenizer;
 
        public static int pars(String x) {
            int num = 0;
            int i = 0;
            if (x.charAt(0) == '-') {
                i = 1;
            }
            for (; i < x.length(); i++) {
                num = num * 10 + (x.charAt(i) - '0');
            }
 
            if (x.charAt(0) == '-') {
                return -num;
            }
 
            return num;
        }
 
        static void init(InputStream input) {
            reader = new BufferedReader(
                    new InputStreamReader(input));
            tokenizer = new StringTokenizer("");
        }
 
        static void init(FileReader input) {
            reader = new BufferedReader(input);
            tokenizer = new StringTokenizer("");
        }
 
        static String next() throws IOException {
            while (!tokenizer.hasMoreTokens()) {
                tokenizer = new StringTokenizer(
                        reader.readLine());
            }
            return tokenizer.nextToken();
        }
 
        static int nextInt() throws IOException {
            return pars(next());
        }
 
        static long nextLong() throws IOException {
            return Long.parseLong(next());
        }
 
        static double nextDouble() throws IOException {
            return Double.parseDouble(next());
        }
    } 

class pair implements Comparable<pair>
	{
		long first, second;

     pair() {
    }
     
              
                 
                
		pair(long a, long b)
		{
			first= a;  second = b;
		}

   
		public int compareTo(pair q)
		{
			if(first>q.first)
      return 1;
      else if(first<q.first)
      return -1;
      if( second>q. second)
      return 1;
      else if( second<q. second)
        return -1;
      return 0;
		}	
	}