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.Arrays;
import java.util.Scanner;
import java.util.HashMap;
public class Main {
public static void main(String[] args) {
		Scanner scn  = new Scanner(System.in);
		int a = scn.nextInt();
		int b = scn.nextInt();
		
		HashMap<Integer,Integer> map = new HashMap<>();
		for(int i=0;i<b;i++) {
			map.put(scn.nextInt(), 1);
		}
		int p=Integer.MAX_VALUE;
		int q=Integer.MAX_VALUE;
		for(int i=a;i>0;i--) {
			if(!map.containsKey(i)) {
				p=a-i;
				break;
			}
		}
		for(int i=a+1;i<=100;i++) {
			if(!map.containsKey(i)) {
				 q=i-a;
				break;
			}
		}
		if(p<=q) {
			System.out.println(a-p);
		}
		else {
			System.out.println(a+q);
		}
 
	}
 
}