/*
 * Solution Template for Distincto's Raffle
 * 
 * Australian Informatics Olympiad 2023
 * 
 * This file is provided to assist with reading of input and writing of output 
 * for the problem. You may modify this file however you wish, or
 * you may choose not to use this file at all.
 */

import java.io.*;

class Solution {

    /* N is the number of competitors. */
    private static int N;

    /* Competitors all submit a number between 1 and K inclusive. */
    private static int K;

    /* numbers contains the submitted numbers. */
    private static int numbers[] = new int[100005];

    private static int answer;
    /*
     * Read the next token from the input file.
     * Tokens are separated by whitespace, i.e., spaces, tabs and newlines.
     * If end-of-file is reached then an empty string is returned.
     */
    private static String readToken(BufferedReader in) throws IOException {
        StringBuffer ans = new StringBuffer();
        int next;

        /* Skip any initial whitespace. */
        next = in.read();
        while (next >= 0 && Character.isWhitespace((char)next))
            next = in.read();

        /* Read the following token. */
        while (next >= 0 && ! Character.isWhitespace((char)next)) {
            ans.append((char)next);
            next = in.read();
        }

        return ans.toString();
    }

    public static void main(String[] args) throws IOException {
        /* Open the input and output streams for stdin and stdout. */
        BufferedReader input_reader = new BufferedReader(new InputStreamReader(
                System.in));
        BufferedWriter output_writer = new BufferedWriter(
                new OutputStreamWriter(System.out));
        /* Read the values of N, K and the submitted numbers. */
        N = Integer.parseInt(readToken(input_reader));
        K = Integer.parseInt(readToken(input_reader));
        for (int i = 0; i < N; i++) {
            numbers[i] = Integer.parseInt(readToken(input_reader));
        }

        /*
         * TODO: This is where you should compute your solution. Store the
         * winning number, or -1 if there is no winning number, into the
         * variable answer.
         */

        /* Write the answer. */
        output_writer.write(answer + "\n");

        /* Close the input_reader and output_writer. */
        input_reader.close();
        output_writer.close();
    }
}