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: Accepted)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashSet;
import java.util.Set;

public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		String str[] = br.readLine().split(" ");

		int x = Integer.parseInt(str[0]);
		int n = Integer.parseInt(str[1]);

		if (n == 0) {
			System.out.println(x);
			return;
		}

		Set<Integer> p = new HashSet<>();

		str = br.readLine().split(" ");
		for (int i = 0; i < n; i++) {
			p.add(Integer.parseInt(str[i]));
		}

		if (!p.contains(x)) {
			System.out.println(x);
			return;
		}

		for (int i = 1; i <= 200; i++) {
			int left = Math.abs(x - i);
			int right = Math.abs(x + i);

			if (!p.contains(left) && p.contains(right)) {
				System.out.println(left);
				return;
			} else if (p.contains(left) && !p.contains(right)) {
				System.out.println(right);
				return;
			} else if (!p.contains(left) && !p.contains(right)) {
				System.out.println(left);
				return;
			}
		}
	}
}