Resizable Array

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Resizable_Array
{
    class Program
    {
        static void Main()
        {
            long?[] arr = new long?[4];
            string[] command = Console.ReadLine().Split();

            while (command[0] != "end")
            {
                switch (command[0])
                {
                    case "push":
                        for (long i = 0; i < arr.Length; i++)
                        {
                            if (arr[i]==null)
                            {
                                arr[i] = long.Parse(command[1]);
                                break;
                            }
                            if (arr[arr.Length-1] != null)
                            {
                                long?[] arrBuffer = new long?[arr.Length];
                                Array.Copy(arr, arrBuffer, arrBuffer.Length);
                                arr = new long?[arr.Length * 2];
                                Array.Copy(arrBuffer, arr, arrBuffer.Length);
                            }
                        }
                        break;
                    case "pop":
                        for (long i = arr.Length-1; i >= 0; i--)
                        {
                            if (arr[i] != null)
                            {
                                arr[i] = null;
                                break;
                            }
                        }
                        break;
                    case "removeAt":
                        long index = long.Parse(command[1]);
                        arr[index] = null;
                        for (long i = index; i < arr.Length-1; i++)
                        {
                            if (arr[i+1] != null)
                            {
                                arr[i] = arr[i + 1];
                            }
                            else
                            {
                                arr[i] = null;
                                break;
                            }
                        }
                        break;
                    case "clear":
                        for (long i = 0; i < arr.Length; i++)
                        {
                            arr[i] = null;
                        }
                        break;
                    default:
                        break;
                }
                command = Console.ReadLine().Split();
            }
            if (arr.All(x => x == null))
            {
                Console.WriteLine("empty array");
                return;
            }
            else
            {
                for (long i = 0; i < arr.Length; i++)
                {
                    if (arr[i] != null)
                    {
                        Console.Write("{0} ",arr[i]);
                    }
                    else
                    {
                        break;
                    }
                }
            }
            Console.WriteLine();
        }
    }
}