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.Linq;

namespace atcoder.abc170.c
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] inputArray = getIntParams();
            int X = inputArray[0];
            int N = inputArray[1];

            int ret = 0;
            if (N == 0)
            {
                ret = X;
            }
            else
            {
                int[] paramArray = getIntParams();

                if (!paramArray.Contains(X))
                {
                    ret = X;
                }
                else
                {
                    for (int i = 1; i <= 100; i++)
                    {
                        if (!paramArray.Contains(X - i))
                        {
                            ret = X - i;
                            break;
                        }
                        if (!paramArray.Contains(X + i))
                        {
                            ret = X + i;
                            break;
                        }
                    }
                }
            }
            Console.WriteLine(ret);
        }

        //↓↓↓ shared function ↓↓↓
        static int getIntParam()
        {
            return int.Parse(Console.ReadLine());
        }
        static int[] getIntParams()
        {
            return Console.ReadLine().Split(' ').Select(i => int.Parse(i)).ToArray();
        }
        static long getLongParam()
        {
            return long.Parse(Console.ReadLine());
        }
        static long[] getLongParams()
        {
            return Console.ReadLine().Split(' ').Select(i => long.Parse(i)).ToArray();
        }
        static string getStringParam()
        {
            return Console.ReadLine();
        }
        static string[] getStringParams()
        {
            return Console.ReadLine().Split(' ');
        }
    }
}