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-mcs 6.8.0.105) (judge verdict: Accepted)

using static System.Math;
using static System.Console;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace AtCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var line = ReadLine().Split(' ').Select(value => long.Parse(value)).ToArray();
            var x = line[0];
            var n = line[1];
            var str = ReadLine();
            if (n == 0)
            {
                WriteLine(x);
                return;
            }
            var nums = str.Split(' ').Select(value => long.Parse(value)).ToArray();

            var contains = new bool[101];
            foreach(var value in nums)
            {
                contains[value] = true;
            }

            var nearest = Abs(0 - x) <= Abs(101 - x) ? 0 : 101;
            for(var i = 1; i <= 100; i++)
            {
                if(!contains[i] && (Abs(x - nearest) > Abs(x - i) || (Abs(x - nearest) == Abs(x - i) && nearest > i)))
                {
                    nearest = i;
                }
            }

            WriteLine(nearest);
        }
    }
}