using System;

public class HappyNumber  

{  

    //isHappyNumber() will determine whether a number is happy or not  

    public static int isHappyNumber(int num){  

        int rem = 0, sum = 0;  

        //Calculates the sum of squares of digits  

        while(num > 0){  

            rem = num%10;  

            sum = sum + (rem*rem);  

            num = num/10;  

        }  

        return sum;  

    }  

    public static void Main()  

    {   

        int number;

        String inputNumber;

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

        inputNumber = Console.ReadLine();

        if (Int32.TryParse(inputNumber, out number) == true){

            while(number != 1 && number != 4){  

            number = isHappyNumber(number);  

        }  

        //Happy number always ends with 1  

        if(number == 1)  

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

        //Unhappy number ends in a cycle of repeating numbers which contains 4  

        else if(number == 4)  

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

        }

    }    

}