//Salvador, Francis Mark C.

//Fabon, Arvin Laynard P.

//CCP 1103 - SECTION

//HAPPY NUMBER

using System;

namespace HappyNumber

{

    public class HappyNumber

    {

        public static void Main()

        {

            int num = 0;

            string userInput;

            Console.WriteLine("Happy Number. ");

            do

            {

                Console.Write("Enter a number: ");

                userInput = Console.ReadLine();

                if (Int32.TryParse(userInput, out num) == true)

                {

                    int result = num;

                    if (0 < num)

                    {

                        if (num <= 20000)

                        {

                            while (result != 1 && result != 4)

                            {

                                result = happyNum(result);

                            }

                            if (result == 1)

                            {

                                Console.WriteLine(num + " is a happy number. ");

                            }

                            else if (result == 4)

                            {

                                Console.WriteLine(num + " is not a happy number. ");

                            }

                            else

                            {

                                Console.WriteLine(" ... ");

                            }

                        }

                        else

                        {

                            Console.WriteLine("Allowed input is only from 1 to 20,000. ");

                        }

                    }

                    else

                    {

                        Console.WriteLine("Zero or negative input is not allowed. ");

                    }

                }

            } while(num > 20000 || num < 1);

        }

        public static int happyNum(int num)

        {

            int sum = 0;

            int modulo = 0;

            while (num > 0)

            {

                modulo = num % 10;

                sum = sum + (modulo * modulo);

                num = num / 10;

            }

            return sum;

        }

    }

}