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.util.ArrayList;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scanner = new Scanner(System.in);
		int X = scanner.nextInt();
		int N = scanner.nextInt();
		ArrayList<Integer> list = new ArrayList<>();
		int answer1 = 0;
		int answer2 = 0;
		int k = 1;
		int m = 1;

		int i = 0;
		while (i < N) {
			int p = scanner.nextInt();
			list.add(p);
			i ++;
		}

		for (int j = 0; j < N; j ++) {
			int after = X - k;

			boolean bool = (list.contains(after));
			System.out.println(bool);

			if (!list.contains(after)) {
				answer1 = after;
				System.out.println(answer1);
				break;
			}
			k++;
		}

		 for (int l = 0; l < N; l++){
			int after2 = X + m;
			if (!list.contains(after2)) {
				answer2 = after2;
				System.out.println(answer2);
				break;
			}
			m++;
		}

		int abs1 = Math.abs(X - answer1);
		int abs2 = Math.abs(X - answer2);

		System.out.println(abs1 < abs2 ? answer1 : answer2);
	}

}