Number 1...100 To Text

using System;
using System.Linq;
using System.Text;

class Program
{
    static void Main()
    {

        //string number = "38";
        string number = Console.ReadLine();
        string[] explode = number.Select(c => c.ToString()).ToArray();

        if (number == "100")
        {
            Console.WriteLine("one hundred");
        }
        else if (number == "0")
        {
            Console.WriteLine("zero");
        }
        else if (number == "1")
        {
            Console.WriteLine("one");
        }
        else if (number == "2")
        {
            Console.WriteLine("two");
        }
        else if (number == "3")
        {
            Console.WriteLine("three");
        }
        else if (number == "4")
        {
            Console.WriteLine("four");
        }
        else if (number == "5")
        {
            Console.WriteLine("five");
        }
        else if (number == "6")
        {
            Console.WriteLine("six");
        }
        else if (number == "7")
        {
            Console.WriteLine("seven");
        }
        else if (number == "8")
        {
            Console.WriteLine("eight");
        }
        else if (number == "9")
        {
            Console.WriteLine("nine");
        }
        else if (number == "10")
        {
            Console.WriteLine("ten");
        }
        else if (number == "11")
        {
            Console.WriteLine("eleven");
        }
        else if (number == "12")
        {
            Console.WriteLine("twelve");
        }
        else if (number == "13")
        {
            Console.WriteLine("thirteen");
        }
        else if (number == "14")
        {
            Console.WriteLine("fourteen");
        }
        else if (number == "15")
        {
            Console.WriteLine("fifteen");
        }
        else if (number == "16")
        {
            Console.WriteLine("sixteen");
        }
        else if (number == "17")
        {
            Console.WriteLine("seventeen");
        }
        else if (number == "18")
        {
            Console.WriteLine("eighteen");
        }
        else if (number == "19")
        {
            Console.WriteLine("nineteen");
        }
        else if (number == "20")
        {
            Console.WriteLine("twenty");
        }

        if (explode[0] == "2" && explode.Length == 2)  //TWENTIES
        {
            Console.Write("twenty");
            if (explode[1] == "1")
            {
                Console.Write(" one");
            }
            else if (explode[1] == "2")
            {
                Console.Write(" two");
            }
            else if (explode[1] == "3")
            {
                Console.Write(" three");
            }
            else if (explode[1] == "4")
            {
                Console.Write(" four");
            }
            else if (explode[1] == "5")
            {
                Console.Write(" five");
            }
            else if (explode[1] == "6")
            {
                Console.Write(" six");
            }
            else if (explode[1] == "7")
            {
                Console.Write(" seven");
            }
            else if (explode[1] == "8")
            {
                Console.Write(" eight");
            }
            else if (explode[1] == "9")
            {
                Console.Write(" nine");
            }
        }
        if (explode[0] == "3" && explode.Length == 2)  //THIRTIES
        {
            Console.Write("thirty");
            if (explode[1] == "1")
            {
                Console.Write(" one");
            }
            else if (explode[1] == "2")
            {
                Console.Write(" two");
            }
            else if (explode[1] == "3")
            {
                Console.Write(" three");
            }
            else if (explode[1] == "4")
            {
                Console.Write(" four");
            }
            else if (explode[1] == "5")
            {
                Console.Write(" five");
            }
            else if (explode[1] == "6")
            {
                Console.Write(" six");
            }
            else if (explode[1] == "7")
            {
                Console.Write(" seven");
            }
            else if (explode[1] == "8")
            {
                Console.Write(" eight");
            }
            else if (explode[1] == "9")
            {
                Console.Write(" nine");
            }
        }
        if (explode[0] == "4" && explode.Length == 2)  // fourTIES
        {
            Console.Write("fourty");
            if (explode[1] == "1")
            {
                Console.Write(" one");
            }
            else if (explode[1] == "2")
            {
                Console.Write(" two");
            }
            else if (explode[1] == "3")
            {
                Console.Write(" three");
            }
            else if (explode[1] == "4")
            {
                Console.Write(" four");
            }
            else if (explode[1] == "5")
            {
                Console.Write(" five");
            }
            else if (explode[1] == "6")
            {
                Console.Write(" six");
            }
            else if (explode[1] == "7")
            {
                Console.Write(" seven");
            }
            else if (explode[1] == "8")
            {
                Console.Write(" eight");
            }
            else if (explode[1] == "9")
            {
                Console.Write(" nine");
            }
        }
        if (explode[0] == "5" && explode.Length == 2)  //FIFTIES
        {
            Console.Write("fifty");
            if (explode[1] == "1")
            {
                Console.Write(" one");
            }
            else if (explode[1] == "2")
            {
                Console.Write(" two");
            }
            else if (explode[1] == "3")
            {
                Console.Write(" three");
            }
            else if (explode[1] == "4")
            {
                Console.Write(" four");
            }
            else if (explode[1] == "5")
            {
                Console.Write(" five");
            }
            else if (explode[1] == "6")
            {
                Console.Write(" six");
            }
            else if (explode[1] == "7")
            {
                Console.Write(" seven");
            }
            else if (explode[1] == "8")
            {
                Console.Write(" eight");
            }
            else if (explode[1] == "9")
            {
                Console.Write(" nine");
            }
        }
        if (explode[0] == "6" && explode.Length == 2)  // sixTIES
        {
            Console.Write("sixty");
            if (explode[1] == "6")
            {
                Console.Write(" one");
            }
            else if (explode[1] == "2")
            {
                Console.Write(" two");
            }
            else if (explode[1] == "3")
            {
                Console.Write(" three");
            }
            else if (explode[1] == "4")
            {
                Console.Write(" four");
            }
            else if (explode[1] == "5")
            {
                Console.Write(" five");
            }
            else if (explode[1] == "6")
            {
                Console.Write(" six");
            }
            else if (explode[1] == "7")
            {
                Console.Write(" seven");
            }
            else if (explode[1] == "8")
            {
                Console.Write(" eight");
            }
            else if (explode[1] == "9")
            {
                Console.Write(" nine");
            }
        }
        if (explode[0] == "7" && explode.Length == 2)  // sevenTIES
        {
            Console.Write("seventy");
            if (explode[1] == "1")
            {
                Console.Write(" one");
            }
            else if (explode[1] == "2")
            {
                Console.Write(" two");
            }
            else if (explode[1] == "3")
            {
                Console.Write(" three");
            }
            else if (explode[1] == "4")
            {
                Console.Write(" four");
            }
            else if (explode[1] == "5")
            {
                Console.Write(" five");
            }
            else if (explode[1] == "6")
            {
                Console.Write(" six");
            }
            else if (explode[1] == "7")
            {
                Console.Write(" seven");
            }
            else if (explode[1] == "8")
            {
                Console.Write(" eight");
            }
            else if (explode[1] == "9")
            {
                Console.Write(" nine");
            }
        }
        if (explode[0] == "8" && explode.Length == 2)  // eightIES
        {
            Console.Write("eighty");
            if (explode[1] == "1")
            {
                Console.Write(" one");
            }
            else if (explode[1] == "2")
            {
                Console.Write(" two");
            }
            else if (explode[1] == "3")
            {
                Console.Write(" three");
            }
            else if (explode[1] == "4")
            {
                Console.Write(" four");
            }
            else if (explode[1] == "5")
            {
                Console.Write(" five");
            }
            else if (explode[1] == "6")
            {
                Console.Write(" six");
            }
            else if (explode[1] == "7")
            {
                Console.Write(" seven");
            }
            else if (explode[1] == "8")
            {
                Console.Write(" eight");
            }
            else if (explode[1] == "9")
            {
                Console.Write(" nine");
            }
        }
        if (explode[0] == "9" && explode.Length == 2)  // nineTIES
        {
            Console.Write("ninety");
            if (explode[1] == "1")
            {
                Console.Write(" one");
            }
            else if (explode[1] == "2")
            {
                Console.Write(" two");
            }
            else if (explode[1] == "3")
            {
                Console.Write(" three");
            }
            else if (explode[1] == "4")
            {
                Console.Write(" four");
            }
            else if (explode[1] == "5")
            {
                Console.Write(" five");
            }
            else if (explode[1] == "6")
            {
                Console.Write(" six");
            }
            else if (explode[1] == "7")
            {
                Console.Write(" seven");
            }
            else if (explode[1] == "8")
            {
                Console.Write(" eight");
            }
            else if (explode[1] == "9")
            {
                Console.Write(" nine");
            }
        }

        if (number != "0" && number != "100" && number != "1" && number != "2" && number != "3" && number != "4" && number != "5" && number != "6" && number != "7" && number != "8" && number != "9" && number != "10" && number != "17" && number != "18" && number != "19" && number != "20" && number != "11" && number != "12" && number != "13" && number != "14" && number != "15" && number != "16" && explode.Length != 2 || number == "-1")
        {
            Console.WriteLine("invalid number");
        }
    }
}