Problem:
Score : 300 points

Problem Statement

Given are an integer X and an integer sequence of length N: p_1, \ldots, p_N.

Among the integers not contained in the sequence p_1, \ldots, p_N (not necessarily positive), find the integer nearest to X, that is, find the integer whose absolute difference with X is the minimum. If there are multiple such integers, report the smallest such integer.

Constraints

1 \leq X \leq 100

0 \leq N \leq 100

1 \leq p_i \leq 100

p_1, \ldots, p_N are all distinct.

All values in input are integers.

Input

Input is given from Standard Input in the following format:

X N
p_1 ... p_N

Output

Print the answer.

Sample Input 1

6 5
4 7 10 6 5

Sample Output 1

8

Among the integers not contained in the sequence 4, 7, 10, 6, 5, the one nearest to 6 is 8.

Sample Input 2

10 5
4 7 10 6 5

Sample Output 2

9

Among the integers not contained in the sequence 4, 7, 10, 6, 5, the ones nearest to 10 are 9 and 11. We should print the smaller one, 9.

Sample Input 3

100 0

Sample Output 3

100

When N = 0, the second line in the input will be empty. Also, as seen here, X itself can be the answer.

Solution in Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)

import java.io.*;
import java.util.*;
import static java.lang.System.out;

public class Main{
    static MyReader in = new MyReader();

    public static void main(String[] args){
        int X = in.i();
        int N = in.i();
        int[] p = in.ii(N);

        boolean[] b = new boolean[101];
        for (int i = 0; i < N; i++) {
            b[p[i]] = true;
        }

        int ans = X;
        if (b[X]) {
            ans = 0;
            for (int i = X - 1; i > 0; i--) {
                if (!b[i]) {
                    ans = i;
                    break;
                }
            }
            for (int i = X + 1; i < 101; i++) {
                if (!b[i]) {
                    if (i - X < X - ans) {
                        ans = i;
                    }
                    break;
                }
            }
        }
        out.println(ans);
    }

    static class MyReader extends BufferedReader {
        char[] cbuf = new char[1024];
        int head = 0;
        int tail = 0;

        MyReader() {
            super(new InputStreamReader(System.in));
        }

        char next() {
            if (head == tail) {
                try {
                    tail = read(cbuf, 0, cbuf.length);
                } catch (IOException e) {}
                head = 0;
            }
            return cbuf[head++];
        }

        void back() {
            head--;
        }

        boolean minus() {
            boolean minus;
            while (true) {
                char c = next();
                if (c != ' ' && c != '\n' && c != '\r') {
                    if (!(minus = c == '-')) back();
                    return minus;
                }
            }
        }

        void skip() {
            while (true) {
                char c = next();
                if (c != ' ' && c != '\n' && c != '\r') {
                    back();
                    break;
                }
            }
        }

        char[] s(final int N) {
            skip();
            char[] s = new char[N];
            for (int i = 0; i < s.length; i++) {
                s[i] = next();
            }
            return s;
        }

        int i() {
            boolean minus = minus();
            int n = 0;
            while (true) {
                int k = next() - '0';
                if (k < 0 || 9 < k) break;
                n = 10 * n + k;
            }
            return minus ? -n : n;
        }

        int[] ii(final int N) {
            int[] a = new int[N];
            for (int j = 0; j < a.length; j++) a[j] = i();
            return a;
        }

        long l() {
            boolean minus = minus();
            long n = 0;
            while (true) {
                int k = next() - '0';
                if (k < 0 || 9 < k) break;
                n = 10 * n + k;
            }
            return minus ? -n : n;
        }
    }
}