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# (Mono-csc 3.5.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;

namespace C
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] input1 = Console.ReadLine().Split(" ");
            int X = int.Parse(input1[0]);
            int N = int.Parse(input1[1]);

            string input2_s = Console.ReadLine();
            string[] input2;
            int ans;
            if (!string.IsNullOrEmpty(input2_s))
            {
                input2 = input2_s.Split(" ");

                List<int> p = new List<int>();
                foreach (string element in input2)
                {
                    p.Add(int.Parse(element));
                }

                int ans_l = X;
                for (int i = X; i <= 101; i++)
                {
                    if (!p.Contains(i))
                    {
                        ans_l = i;
                        break;
                    }
                }

                int ans_s = X;
                for (int i = X; i >= 0; i--)
                {
                    if (!p.Contains(i))
                    {
                        ans_s = i;
                        break;
                    }
                }

                if (System.Math.Abs(ans_l - X) > System.Math.Abs(ans_s - X))
                {
                    ans = ans_s;
                }
                else if (System.Math.Abs(ans_l - X) < System.Math.Abs(X - ans_s))
                {
                    ans = ans_l;
                }
                else
                {
                    ans = ans_s;
                }

            }
            else
            {
                ans = X;
            }

            Console.WriteLine(ans);
        }
    }
}