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;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

namespace AtCoder.Abc
{
    class QuestionC
    {
        public static void Main(string[] args)
        {
            var sw = new System.IO.StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(sw);


            // 整数配列の入力
            var ary = Console.ReadLine().Split(' ').Select(i => long.Parse(i)).ToArray();

            var x = ary[0];

            var ps = Console.ReadLine().Split(' ').Where( i => !string.IsNullOrEmpty(i)).Select(i => long.Parse(i)).ToArray();

            long larger = 0;
            for (var i = x; i < 102; i++)
            {
                if(!ps.Contains(i))
                {
                    larger = i;
                    break;
                }
            }

            for(var i = x - 1; i >= -1; i--)
            {
                if (!ps.Contains(i))
                {
                    if( larger - x < x - i)
                    {
                        Console.WriteLine(larger);
                    }
                    else
                    {
                        Console.WriteLine(i);
                    }
                    break ;
                }
            }


            Console.Out.Flush();
        }
    }
}