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.*;

public class Main {

    static ArrayList<Long> a;

    public static void main(String[] args) {

        try (BufferedReader reader = new BufferedReader(new InputStreamReader(System.in))) {

            String[] line = reader.readLine().split(" ");
            int n = Integer.parseInt(line[0]);
            int k = Integer.parseInt(line[1]);
            a = new ArrayList<>();
            line = reader.readLine().split(" ");
            for(int i = 0; i < n; i++) {
                a.add(Long.parseLong(line[i]));
            }
            Collections.sort(a);
            if(n == k) {
                println(1000000000);
                return;
            }
            if(k == 0) {
                if(a.get(0) == 1) println(-1);
                else println(1);
                return;
            }
            int i = k;
            for(; i < n; i++) {
                if(! a.get(i).equals(a.get(k - 1))) {
                    break;
                }
            }
            if(i == k) {
                println(a.get(k - 1));
            } else {
                println(-1);
            }

        } catch (IOException e) {
            println("rerorero");
        }
    }

    static int bin(int num) {
        int l = -1, r = a.size();
        while(r - l > 1) {
            int mid = (r + l) / 2;
            if(a.get(mid) > num) {
                r = mid;
            } else
                l = mid;
        }
        return l;
    }

    static int r(int a, int b) {
        int ans = a / b;
        if(a % b != 0) ans += 1;
        return ans;
    }

    static void print(Object c) {
        System.out.print(c.toString());
    }

    static void println(Object c) {
        System.out.println(c.toString());
    }
}