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.
// package cf977;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.*;
import java.util.concurrent.ThreadLocalRandom;

public class CFC {
    private static final String INPUT = "7 2\n" +
            "3 7 5 1 10 3 20";

    private PrintWriter out;
    private FastScanner sc;

    public static void main(String[] args) {
        new CFC().run();
    }

    public void run() {
        sc = new FastScanner(oj ? System.in : new ByteArrayInputStream(INPUT.getBytes()));
        out = new PrintWriter(System.out);

        long s = System.currentTimeMillis();
        solve();
        out.flush();
        tr(System.currentTimeMillis() - s + "ms");
    }

    public void solve() {
        int n = sc.nextInt();
        int k = sc.nextInt();
        int[] a = readIntArray(n);
//        int[] a = new int[n];
//        Random rnd = new Random();
//        for (int i = 0; i < n; i++) {
//            a[i] = Math.abs(rnd.nextInt());
//        }
        shuffle(a);
        Arrays.sort(a);

        if (k == 0) {
            if (a[0] > 1) {
                out.println(a[0] - 1);
            } else {
                out.println(-1);
            }
        } else if (k == n || a[k-1] < a[k]) {
            out.println(a[k-1]);
        } else {
            out.println(-1);
        }
    }

    //********************************************************************************************
    //********************************************************************************************
    //********************************************************************************************

    private static void shuffle(int[] ar) {
        // If running on Java 6 or older, use `new Random()` on RHS here
        Random rnd = ThreadLocalRandom.current();
        for (int i = ar.length - 1; i > 0; i--) {
            int index = rnd.nextInt(i + 1);
            // Simple swap
            int a = ar[index];
            ar[index] = ar[i];
            ar[i] = a;
        }
    }
    
    private static int lowerBound(long[] arr, long key) {
        int lo = 0;
        int hi = arr.length - 1;
        while (lo < hi) {
            int mid = (lo + hi) / 2;
            if (key <= arr[mid]) {
                hi = mid - 1;
            } else {
                lo = mid + 1;
            }
        }
        return arr[lo] < key ? lo + 1 : lo;
    }

    private static int upperBound(long[] arr, long key) {
        int lo = 0;
        int hi = arr.length - 1;
        while (lo < hi) {
            int mid = (lo + hi) / 2;
            if (key >= arr[mid]) {
                lo = mid + 1;
            } else {
                hi = mid;
            }
        }
        return arr[lo] <= key ? lo + 1 : lo;
    }

    private static int ceil(double d) {
        int ret = (int) d;
        return ret == d ? ret : ret + 1;
    }

    private static int round(double d) {
        return (int) (d + 0.5);
    }

    private static int gcd(int a, int b) {
        BigInteger b1 = BigInteger.valueOf(a);
        BigInteger b2 = BigInteger.valueOf(b);
        BigInteger gcd = b1.gcd(b2);
        return gcd.intValue();
    }

    private static long gcd(long a, long b) {
        BigInteger b1 = BigInteger.valueOf(a);
        BigInteger b2 = BigInteger.valueOf(b);
        BigInteger gcd = b1.gcd(b2);
        return gcd.longValue();
    }

    private int[] readIntArray(int n) {
        int[] res = new int[n];
        for (int i = 0; i < n; i++) {
            res[i] = sc.nextInt();
        }
        return res;
    }

    private long[] readLongArray(int n) {
        long[] res = new long[n];
        for (int i = 0; i < n; i++) {
            res[i] = sc.nextLong();
        }
        return res;
    }

    @SuppressWarnings("unused")
    static class FastScanner {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;

        FastScanner(InputStream stream) {
            this.stream = stream;
        }

        int read() {
            if (numChars == -1)
                throw new InputMismatchException();
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) return -1;
            }
            return buf[curChar++];
        }

        boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        boolean isEndline(int c) {
            return c == '\n' || c == '\r' || c == -1;
        }

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

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

        public double nextDouble() {
            return Double.parseDouble(next());
        }

        public String next() {
            int c = read();
            while (isSpaceChar(c)) c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public String nextLine() {
            int c = read();
            while (isEndline(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isEndline(c));
            return res.toString();
        }

    }

    private boolean oj = System.getProperty("ONLINE_JUDGE") != null;

    private void tr(Object... o) {
        if (!oj) System.out.println(Arrays.deepToString(o));
    }
}