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;

namespace Sample
{
  class Sample
  {
    static void Main(string[] args)
    {
    string[] str1=Console.ReadLine().Split(' ');
    int x=int.Parse(str1[0]);
    int N=int.Parse(str1[1]);
    if(N!=0){
        string[] str2=Console.ReadLine().Split(' ');
        int[] str2ToInt=new int[N];
        int xp=x;
        int xm=x;
        int xpflg=0;
        int xmflg=0;
        
        for(int i=0;i<N;i++){
            str2ToInt[i]=int.Parse(str2[i]);
        }
        while((xpflg==0)&&(xmflg==0)){
            xm--;
            xp++;
            if(!str2ToInt.Contains(xm)){
                xmflg=1;
                break;
            }

            else if(!str2ToInt.Contains(xp)){
                xpflg=1;
                break;
            }
        }
        if(xmflg==1){
            Console.WriteLine(xm);
        }
    
        else  if(xpflg==1){
            Console.WriteLine(xp);
        }
        
    }else{
    Console.WriteLine(x);
    }

           }
  }

}