using System;

​

namespace Nums1to100text

{

    class Nums1to100toText

    {

        static void Main(string[] args)

        {

            int number = int.Parse(Console.ReadLine());

​

            if (number >= 0 && number <= 100)  // checking if the entered number is a valid entry

            {

                // creating a switch that prints the unique numbers and the "teen" numbers - all of these numbers can appear only once in the interval [1; 99]:

                switch (number)

                {

                    case 0: Console.WriteLine("zero"); break;

                    case 10: Console.WriteLine("ten"); break;

                    case 11: Console.WriteLine("eleven"); break;

                    case 12: Console.WriteLine("twelve"); break;

                    case 13: Console.WriteLine("thirteen"); break;

                    case 14: Console.WriteLine("fourteen"); break;

                    case 15: Console.WriteLine("fifteen"); break;

                    case 16: Console.WriteLine("sixteen"); break;

                    case 17: Console.WriteLine("seventeen"); break;

                    case 18: Console.WriteLine("eighteen"); break;

                    case 19: Console.WriteLine("nineteen"); break;

                    case 100: Console.WriteLine("one hundred"); break;

                    default: break;

                }

​

                // creating 2 arrays that contain the values that can appear more than once in the interval [1; 99]:

                string[] tens = { null, null, "twenty", "thirty", "fourty", "fifty", "sixty", "seventy", "eighty", "ninety" };

                string[] ones = { null, "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

​

                if (number > 0 && number < 10) // if the number is between 1 and 9

                {

                    for (int i = 1; i <= ones.Length; i++) // going throug the ones array and prints the string from it (e.g. number = 5 it will print "five" - the fifth element in the array)

                    {

                        if (number == i)

                        {

                            Console.WriteLine(ones[i]);

                        }

                    }

                }

​

                // when the number is from the values that can appear more than once in the interval [1; 99]:

                if (number > 19 && number < 100)

                {

                    int firstNum = number / 10;     // getting the first digit of the number (e.g. 23 / 10 = 2)

                    int secondNum = number % 10;    // getting the second digit of the number (e.g. 23 % 10 = 3)

​

                    for (int i = 1; i <= tens.Length; i++)  // going through the tens array and prints the string from it (e.g. firstNum = 2 it will print "twenty" - the second element of the array)

                    {

                        if (firstNum == i)

                        {

                            Console.Write(tens[i]);

                        }

                    }

                    for (int i = 1; i <= ones.Length; i++) // going throig the ones array and prints the string from it (e.g. secondNum = 3 it will print " three" - the third element of the array)

                    {

                        if (secondNum == i)

                        {

                            Console.WriteLine(" " + ones[i]);

                        }

                    }

                }

            }

            else

            {

                Console.WriteLine("invalid number");  //if (number < 0) or (number > 100)

            }

        }

    }

}

​