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;
using System.Linq;

namespace CSharpSample01
{
	class Program
	{

		static void Main(string[] args)
		{
			var valueList = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
			var X = valueList[0];
			var N = valueList[1];

			var flag = true;
			var count = 1;
			var answer = 0;

			if(N == 0)
			{
				answer = X;
			}
			else
			{
				var numDic = Console.ReadLine().Split(' ').Select(int.Parse).ToDictionary<int, int>(x => x);

				if (!numDic.ContainsKey(X))
				{
					answer = X;
					flag = false;
				}

				while (flag)
				{
					//					if (X - count > 0 && !numDic.ContainsKey(X - count))
					if (!numDic.ContainsKey(X - count))
					{
						answer = X - count;
						flag = false;
					}
					else if (!numDic.ContainsKey(X + count))
					{
						answer = X + count;
						flag = false;
					}
					count++;

					if (count > 100)
					{
						answer = 0;
						flag = false;
					}
				}
			}


			Console.WriteLine(answer);
		}
	}
}