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 1.8.0) (judge verdict: Wrong Answer)

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int target = sc.nextInt();
		int size = sc.nextInt();
		List<Integer> list = new ArrayList<Integer>();

		if(size == 0) {
			System.out.println(target);
			sc.close();
			return;
		}

		for (int i=0;i < size;i++) {
			list.add(sc.nextInt());
		}
		sc.close();

		Collections.sort(list);
		int tmp = list.indexOf(target);

		if(tmp < 0) {
			System.out.println(target);
			return;
		}

		int count = 1;
		int max_tmp = tmp;
		int min_tmp = tmp;
		while(target - count > 0 ||  target + count < list.get(size-1)) {

			min_tmp = list.indexOf(target - count);
			if(min_tmp < 0 && (target - count) > 0) {
				System.out.println(target - count);
				return;
			}

			max_tmp = list.indexOf(target + count);
			if(max_tmp < 0 && (target + count) <= list.get(size-1)) {
				System.out.println(target + count);
				return;
			}

			count++;

		}
		System.out.println(0);
		return;
	}

}