Command interpreter

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

namespace _9.CommandInterpreter
{
    class Program
    {
        static void Main(string[] args)
        {
            List<string> input = Console.ReadLine().Split(new char[] { ' '},StringSplitOptions.RemoveEmptyEntries).ToList();
            string[] command = Console.ReadLine().Split(' ').ToArray();
            while (command[0] != "end")
            {

                if (command[0]=="reverse")
                {
                    int start = int.Parse(command[2]);
                    int count = int.Parse(command[4]);
                    if(IsValidCommand(input,start,count))
                    {
                        List<string> portion = new List<string>();
                        for (int i = start; i < start + count; i++)
                        {
                            portion.Add(input[i]);
                        }
                        portion.Reverse();
                        input.RemoveRange(start, count);
                        input.InsertRange(start, portion);
                    }
                    else
                    {
                        Console.WriteLine("Invalid input parameters.");
                    }
                }
                else if(command[0]=="sort")
                {
                    int start = int.Parse(command[2]);
                    int count = int.Parse(command[4]);
                    if (IsValidCommand(input, start, count))
                    {
                        List<string> portion = new List<string>();
                        for (int i = start; i < start + count; i++)
                        {
                            portion.Add(input[i]);
                        }
                        portion.Sort();
                        input.RemoveRange(start, count);
                        input.InsertRange(start, portion);
                    }
                    else
                    {
                        Console.WriteLine("Invalid input parameters.");
                    }
                }
                else if(command[0] == "rollLeft")
                {
                    int times = int.Parse(command[1]);
                    if (times < 1)
                    {
                        Console.WriteLine("Invalid input parameters.");
                    }
                    else
                    {
                        for (int i = 0; i < times; i++)
                        {
                            List<string> inner = new List<string>();
                            string start = input[0];
                            for (int j = 1; j < input.Count; j++)
                            {
                                inner.Add(input[j]);
                            }
                            inner.Add(start);
                            input = inner;
                        }
                    }
                }
                else if(command[0]== "rollRight")
                {
                    int times = int.Parse(command[1]);
                    if(times<1)
                    {
                        Console.WriteLine("Invalid input parameters.");
                    }
                    else
                    {
                        for (int i = 0; i < times; i++)
                        {
                            List<string> inner = new List<string>();
                            string end = input[input.Count - 1];
                            inner.Insert(0, end);
                            for (int j = 0; j < input.Count - 1; j++)
                            {
                                inner.Add(input[j]);
                            }
                            input = inner;
                        }
                    }
                }
                else
                {
                    Console.WriteLine("Invalid input parameters.");
                }
                command = Console.ReadLine().Split(' ').ToArray();
            }
            string separator = ", ";
            Console.Write("[");
            Console.Write(string.Join(separator,input));
            Console.WriteLine("]");
        }

        static bool IsValidCommand(List<string> input, int start, int count)
        {
            bool result = true;
            if((start<0)||(start>=input.Count-1))
            {
                result = false;
            }
            if((count<0)||(count+start>=input.Count-1))
            {
                result = false;
            }
            return result;
        }
    }
}