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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

class Program
{
    static void Main(string[] args)
    {
        long[] a = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
        long[] flag = new long[101];
        if (a[1] == 0)
        {
            string b = Console.ReadLine();
        }
        else
        {
            long[] b = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();

            for (int i = 0; i < b.Length; i++)
            {
                flag[(int)b[i]] = 1;
            }
        }
        
        long kotae = 0;
        

        if (flag[a[0]] == 0)
        {
            kotae = a[0];
        }
        else if (a[1] == 0)
        {
            kotae = a[0];
        }
        else
        {
            for (int i = 1; i < 100; i++)
            {
                if ((int)a[0] - i >= 0 && (int)a[0] - i <=100)
                {
                    if (flag[(int)a[0] - i] == 0)
                    {
                        kotae = a[0] - (long)i;
                        break;
                    }
                }

                if ((int)a[0] + i < flag.Length && (int)a[0] - i <= 0)
                {
                    if (flag[(int)a[0] + i] == 0)
                    {
                        kotae = a[0] + (long)i;
                        break;
                    }
                }
            }
        }


        Console.WriteLine(kotae);
    }
}