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;

namespace AtCoderMake.ABC170
{
    class ABC170C
    {
        static void Main(string[] args)
        {
            var xn = Console.ReadLine().Split().Select((x) => int.Parse(x)).ToArray();
            
            var pmap = new Dictionary<int,int>();
            int min = 0;
            int max = 101;
            int ans=0;
            if (xn[1] != 0)
            {
                var pi = Console.ReadLine().Split().Select((x) => int.Parse(x)).ToArray();

                foreach (int p in pi)
                {
                    pmap.Add(p, 0);
                }
            }
            for(int i = xn[0]; i >= 0; i--)
            {
                if (pmap.ContainsKey(i)==false)
                {
                    min = i;
                    break;
                }
            }
            for (int i = xn[0]; i <= 101; i++)
            {
                if (pmap.ContainsKey(i)==false)
                {
                    max = i;
                    break;
                }
            }
            if (xn[0] - min > max - xn[0])
            {
                ans = max;
            }
            else
            {
                ans = min;
            }
            Console.WriteLine(ans);
        }
        
    }
}