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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;

namespace PaizaTest
{
    class Program
    {
        static void Main(string[] args)
        {
            var XN = Console.ReadLine().Split().Select(int.Parse).ToList();
            if (XN[1] == 0)
            {
                Console.WriteLine(XN[0]);
                return;
            }
            var p = Console.ReadLine().Split().Select(int.Parse).ToList();

            var nums = new List<int>();

            for (int i = -101; i <= 100; i++)
            {
                if (p.Contains(i))
                {
                    continue;
                }

                nums.Add(i);
            }

            var minimum = int.MaxValue;
            var result = 0;

            foreach (var num in nums)
            {
                if (minimum > Math.Abs(XN[0] - num))
                {
                    minimum = Math.Abs(XN[0] - num);
                    result = num;
                }
            }

            Console.WriteLine(result);
        }
    }
}