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: Runtime Error)

using System;
namespace q1
{
    class q2
    {
        static void Main()
        {
            string[] saisyo = Console.ReadLine().Split();
            int kizyun = int.Parse(saisyo[0]);
            int kosuu = int.Parse(saisyo[1]);
            string[] reigaimae = Console.ReadLine().Split();
            int[] reigai = new int[kosuu];
            for (int henkan = 0;henkan < kosuu;henkan++)
            {
                reigai[henkan] = int.Parse(reigaimae[henkan]);
            }
            Array.Sort(reigai);
            for (int x = 0; x < kosuu; x++)
            {
                if(reigai[x] == kizyun && x < kosuu-1)
                {
                    Console.WriteLine(kizyun);
                    x = kosuu;
                }
                if (reigai[x] > kizyun && x < kosuu-1)
                {
                    if(x == 0)
                    {
                        Console.WriteLine(reigai[0]);
                    }
                    else if(x-reigai[x-1] == reigai[x]-x)
                    {
                        Console.WriteLine(reigai[x - 1]);
                    }
                    else if (x - reigai[x - 1] < reigai[x] - x)
                    {
                        Console.WriteLine(reigai[x - 1]);
                    }
                    else
                    {
                        Console.WriteLine(reigai[x]);
                    }
                    x = kosuu;
                }
                if(x == kosuu-1)
                {
                    Console.WriteLine(reigai[x]);
                }
                else
                {

                }
            }
        }
    }
}