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 AtCoder200531
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] inputs = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
            int[] indexes = null;
            try
            {
                indexes = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
            }
            catch(Exception ex)
            {

            }
            int[] nums = Enumerable.Range(0, 102).ToArray();
            if (indexes != null)
            {
                foreach (int index in indexes)
                {
                    nums[index] = 99999;
                }
                nums = nums.Select(i => Math.Abs(i - inputs[0])).ToArray();

                int min = 99999;
                int minIndex = -1;
                for (int i = 0; i < nums.Length; i++)
                {
                    if (min > nums[i])
                    {
                        min = nums[i];
                        minIndex = i;
                    }
                }
                Console.WriteLine(minIndex);
            }
            else
            {
                Console.WriteLine(inputs[0]);
            }

        }
    }
}