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 {


    public static int cnt(int el, int[] a){
        int cnt = 0;
        for(int x : a) {
            if (x <= el) cnt++;
            else break;
        }
        return cnt;
    }

    public static void main(String[] args) throws IOException, InterruptedException {
        int n = sc.nextInt(), k = sc.nextInt()-1;
        int[] a = sc.nextIntArr(n);

        intSort(a);
        if(k == n-1) pw.println(a[n-1]);
        else if(k == -1){
            if(a[0] > 1) pw.println(1);
            else pw.println(-1);
        }
        else{
//            pw.println(cnt(a[k], a));
            pw.println(cnt(a[k], a) == (k+1) ? a[k] : -1);
        }

        pw.close();

    }

    public static void pairSort(Pair[] arr) {
        ArrayList<Pair> l = new ArrayList<>();
        Collections.addAll(l, arr);
        Collections.sort(l);
        for (int i = 0; i < arr.length; i++) {
            arr[i] = l.get(i);
        }
    }
    public static void longSort(long[] arr) {
        ArrayList<Long> l = new ArrayList<>();
        for (long i : arr) l.add(i);
        Collections.sort(l);
        for (int i = 0; i < arr.length; i++) {
            arr[i] = l.get(i);
        }
    }
    public static void intSort(int[] arr) {
        ArrayList<Integer> l = new ArrayList<>();
        for (int i : arr) l.add(i);
        Collections.sort(l);
        for (int i = 0; i < arr.length; i++) {
            arr[i] = l.get(i);
        }
    }

    static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public String next() throws IOException {
            while (st == null || !st.hasMoreTokens())
                st = new StringTokenizer(br.readLine());
            return st.nextToken();
        }

        public int nextInt() throws IOException {
            return Integer.parseInt(next());
        }

        public long nextLong() throws IOException {
            return Long.parseLong(next());
        }

        public String nextLine() throws IOException {
            return br.readLine();
        }

        public double nextDouble() throws IOException {
            String x = next();
            StringBuilder sb = new StringBuilder("0");
            double res = 0, f = 1;
            boolean dec = false, neg = false;
            int start = 0;
            if (x.charAt(0) == '-') {
                neg = true;
                start++;
            }
            for (int i = start; i < x.length(); i++)
                if (x.charAt(i) == '.') {
                    res = Long.parseLong(sb.toString());
                    sb = new StringBuilder("0");
                    dec = true;
                } else {
                    sb.append(x.charAt(i));
                    if (dec)
                        f *= 10;
                }
            res += Long.parseLong(sb.toString()) / f;
            return res * (neg ? -1 : 1);
        }

        public boolean ready() throws IOException {
            return br.ready();
        }

        public int[] nextIntArr(int n) throws IOException {
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = Integer.parseInt(next());
            }
            return arr;
        }

        public long[] nextLongArr(int n) throws IOException {
            long[] arr = new long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = Long.parseLong(next());
            }
            return arr;
        }

    }
    static class Pair implements Comparable<Pair>{
        int first; int second; int length;
        public Pair(int first, int second){
            this.first = first; this.second = second; this.length = second-first+1;
        }

        @Override
        public int compareTo(Pair p2) {
            if(first == p2.first) return second - p2.second;
            else return first - p2.first;
        }

        @Override
        public String toString() { return "("+ first + "," + second + ')'; }

    }
    static class Triple implements Comparable<Triple> {
        double x, y, z, sum;

        Triple(double a, double b, double c) { x = a; y = b; z = c; sum = x + y + z; }


        public int compareTo(Triple t)
        {
            if(Math.abs(sum - t.sum) < 1e-9) return x > t.x ? 1 : -1;
            return sum > t.sum ? 1 : -1;
        }
        public String toString()
        {
            return x + " " + y  + " " + z;
        }
    }

    static PrintWriter pw = new PrintWriter(System.out);
    static Scanner sc = new Scanner(System.in);
    static Random random = new Random();
    static final int MOD = (int) 1e9 + 7;
}