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;
class Program
{
    static void Main(string[] args)
    {
        string[] input1 = Console.ReadLine().Split(' ');
        int x = int.Parse(input1[0]);
        int n = int.Parse(input1[1]);

        string[] input2 = Console.ReadLine().Split(' ');
        /*
        int[] p = new int[] { };
        for(var i =0;i<n;i++)
        {
            p[i] = int.Parse(input2[i]);
        }
        */
        int[] nums = new int[101];
        for (var i = 0; i<=100;i++)
        {
            nums[i] = i;
        }
        /*
        int[] numnum = new int[] { };
        numnum = nums;
        numnum.Concat(p).ToArray();

        Dictionary<int, int> dic = new Dictionary<int, int> { };
        */

        for (var i = 0; i <= 100; i++)
        {
            for (var j = 0; j < n; j++)
            {
                if(nums[i] == int.Parse(input2[j]))
                {
                    nums[i] = 200;
                    break;
                }
            }

        }
        /*
        int[] p = new int[101];
        for (var i = 0; i < n; i++)
        {
            p[i] = int.Parse(nums[i]);
        }*/

        int[] p2 = nums.Select(i => Math.Abs(i - x)).ToArray();

        int absMin = 100;
        int noMin = x;

        for(var i = 0; i<=100; i++)
        {
            if(absMin > p2[i])
            {
                absMin = p2[i];
                noMin = i;
            }
        }

        Console.WriteLine(noMin);

    }
}