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;
 
namespace lean {
    class Program {
        static void Main() {
            int[] a = Console.ReadLine().Split().Select(int.Parse).ToArray();
            int x = a[0];
            int[] lis = new int[] { };
            if (a[1] == 0)
            {
                Console.WriteLine(a[0]);
                Environment.Exit(0);
            }

            int[] result = lis.Concat(new int[] { a[0] }).ToArray();

            for (int i = 0; i <= 50; i++)
            {
                if (!result.Contains(a[0] - i))
                {
                    Console.WriteLine(a[0] - i);
                    return;
                }
                if(!result.Contains(a[0] + i)) {
                    Console.WriteLine(a[0] + i);
                    return;
                }
            }

        }
    }
}