using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

​

        string[] array = {"2", "1", "1", "2", "3", "3", "2", "2", "2", "1"};

        string previous = string.Empty;

        List<string> sequence = new List<string>();

        List<string> tempSequence = new List<string>();

        for (int i = 0; i < array.Length; i++)

        {

            if (array[i] != previous)

            {

                tempSequence.Add(previous);

                if (tempSequence.Count > sequence.Count)

                {

                    sequence = new List<string>(tempSequence);

                }

                tempSequence.Clear();

            }

            else

            {

                tempSequence.Add(previous);

            }

            previous = array[i];

        }

        Console.WriteLine(string.Join(", ", sequence));

    }

}