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 AtCoder
{
  public class Program
  {
    static bool finded = false;

    static void Main(string[] args)
    {
      string[] xn = Console.ReadLine().Split(" ");
      string[] data = Console.ReadLine().Split(" ");
      int x = int.Parse(xn[0]);
      int n = int.Parse(xn[1]);
      int[] nums = new int[n];

      for (int i=0; i<n; i++)
      {
        nums[i] = int.Parse(data[i]);
      }

      for (int i=x; i>0; i--)
      {
        if (finded == false)
        {
          judge(nums, nums[i]);
        }
        else
        {
          break;
        }
      }
      for (int i=x; i<100; i++)
      {
        if (finded == false)
        {
          judge(nums, nums[i]);
        }
        else
        {
          break;
        }
      }
    }

    static void judge(int[] nums, int num)
    {
      for (int i=0; i<nums.Length; i++)
      {
        if (nums[i] == num)
        {
          return;
        }
        else
        {
          finded = true;
          Console.Write(num);
        }
      }
    }
  }
}