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;

class Program
{
  static string _trigger;
  static int _margin = 0;
  static string _str;
  static int[] p;
  static int n;
  static void Main()
  {
    var line = Console.ReadLine();
    var _line = line.Split(" ");
    int x = int.Parse(_line[0]);
    n = int.Parse(_line[1]);
    if (n == 0)
    {
      Console.WriteLine(x);
      return;
    }
    p = new int[n];
    line = Console.ReadLine();
    _line = line.Split(" ");
    
    for (int i = 0; i < n; i++)
    {
      p[i] = int.Parse(_line[i]);
      _str += p[i].ToString();
    }
    while(_trigger == null)
    {
      _trigger = Judge(x - _margin);
      if (_trigger == null)
        _trigger = Judge(x + _margin);
      _margin++;
    }
    Console.WriteLine(int.Parse(_trigger));
  }
  
  static String Judge(int _num)
  {
    for (int i = 0; i < n; i++)
    {
      if (_num == p[i])
      {
        return null;
      }
    }
    return _num.ToString();
  }
}