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)

//package ABC170;
import java.util.*;
import java.io.*;
import java.lang.*;
class Main {

	public static void main(String[] args) {
		Scanner sc =new Scanner(System.in);
		int x=sc.nextInt();
		int n=sc.nextInt();
		HashSet<Integer> hs=new HashSet<>();
		for(int i=0;i<n;i++)
		{
			hs.add(sc.nextInt());
		}
		if(hs.contains(x)==false)
		{
			System.out.println(x);
			return;
		}
		int num1=x-1;
		int num2=x+1;
		while(true)
		{
			if(hs.contains(num1)==false)
			{
				System.out.println(num1);
				return;
			}
			else
			{
				num1--;
			}
			if(hs.contains(num2)==false)
			{
				System.out.println(num2);
				return;
			}
			else
			{
				num2++;
			}
		}

	}

}