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 C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;

class Program
{
	static void Main(string[] args)
	{
		string[] strInput = Console.ReadLine().Split(' '); ;
		int x = int.Parse(strInput[0]);
		int n = int.Parse(strInput[1]);
		strInput = Console.ReadLine().Split(' '); ;
		int[] p = new int[n];

		Dictionary<int, int> dict = new Dictionary<int, int>();

		for (int i = 0; i < n; i++)
		{
			p[i] = int.Parse(strInput[i]);
			dict.Add(p[i], 1);
		}
		if(dict.ContainsKey(x) == false)
		{
			Console.WriteLine(x);
			return;
		}
		
		for (int i = 1; i < 100; i++)
		{
			if (dict.ContainsKey(x - i) == false)
			{
				Console.WriteLine(x - i);
				return;
			}
			if (dict.ContainsKey(x + i) == false)
			{
				Console.WriteLine(x + i);
				return;
			}

		}

		return;
	}
}