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;

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]);
    string[] str2=Console.ReadLine().Split(' ');
    
      if(N!=0){
          int[] str2ToInt=new int[N];

          for(int i=0;i<N;i++){
              str2ToInt[i]=int.Parse(str2[i]);
          }

          int[] str3ToInt=new int[str2ToInt.Max() - str2ToInt.Min() + 3];
          int j = 0;

          for(int ii=str2ToInt.Min()-1;ii<str2ToInt.Max()+2;ii++){
            if(!str2ToInt.Contains(ii)){
              str3ToInt[j]=ii;
              j = j + 1;
            }
          }

          int str3_num = j;

          //コピー先の配列を作成する
          int[] ary2 = new int[str3_num];
          //指定された範囲をコピーする
          Array.Copy(str3ToInt, 0, ary2, 0, str3_num);

          int[] ary3 = new int[str3_num];
          for(int l=0;l<ary3.Length;l++){
              ary3[l] = System.Math.Abs(ary2[l] - x);
          }

          Console.WriteLine( ary2.Where(num => System.Math.Abs(num - x) == ary3.Min()).Min() );

      }else{
        Console.WriteLine(x);
      }
   }
  }

}