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.Linq;
    using System.Collections.Generic;
    using System.IO;
    using System.Text;
    using System.Text.RegularExpressions;

    class Program
    {
        static void Main()
        {
            var inputList = System.Console.ReadLine().Split(' ').Select((x) => decimal.Parse(x)).ToList();
            var x = inputList[0];
            var n = inputList[1];
            if (n == 0)
            {
                Output(x.ToString());
                return;
            }
            try
            {
                var pList = System.Console.ReadLine().Split(' ').Select((x) => decimal.Parse(x)).ToList();

                var minList = pList.OrderBy(c => Math.Abs(c - x)).ToList();
                for (int i = 0; i < n + 1; i++)
                {
                    var target = x;
                    target = x - i;
                    if (!pList.Contains(target))
                    {
                        Output(target.ToString());
                        return;
                    }
                    target = x + i;
                    if (!pList.Contains(target))
                    {
                        Output(target.ToString());
                        return;
                    }
                }
                Output(x.ToString());
            }

            catch
            {
                Output(x.ToString());
            }
        }
        private static void Output(string str)
        {
            var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(sw);

            Console.WriteLine(str);

            Console.Out.Flush();
        }
    }