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

namespace ConsoleAppAtCoderABC170
{
    class Program
    {
        static void Main(string[] args)
        {
            var xn = ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
            var (x, n) = (xn[0], xn[1]);
            var p = ReadLine().Split(' ').Select(s => { if (int.TryParse(s, out int n)) { return n; } else { return -1; } }).ToArray();

            var ans = Enumerable.Range(0, 102).Except(p).OrderBy(n => Math.Abs(x - n)).ThenBy(n => n).First();

            WriteLine(ans);
        }
    }
}