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: Wrong Answer)

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

class Program
{
    static void Main(string[] args)
    {
        Program pg = new Program();
        Console.WriteLine(pg.Exe());
    }

    public int Exe()
    {
        int[] input = Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse);
        int target_val = input[0];
        int answer = target_val;
        int num_cnt = input[1];

        //数列の長さが0の場合、目標値が答えとなるので返す
        if(num_cnt == 0) return answer;
        else answer = 999999;

        List<int> num_list = new List<int>(100);
        for(int i = 0; i <= 100;i++)
        {
            num_list.Add(i);
        }

        List<int> exclusion_numlist = new List<int>(Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse));
        IEnumerable<int> results = num_list.Except(exclusion_numlist);

        int temp = 0;
        int temptgt = answer - target_val;
        foreach(int i in results)
        {
            temp = Math.Abs(i - target_val);
            if(temptgt > temp)
            {
                answer = i;
                temptgt = temp;
            }
            else if(temptgt == temp && answer > i)
            {
                answer = i;
                temptgt = temp;
            }
        }

        return answer;
    }
}