using System;

​

//1. Write a program which finds the factorial of a number entered by the user.

​

namespace Beginner1{

​

public class ProblemOne

{

    public static void Main(string[] args)

    {

        bool play = true;

        while ( play ) {

            Console.Write ("Type in the number you would like to find Factorial of: ");

            int num = Convert.ToInt16( Console.ReadLine ());

            int sum = 1;

            for (int i = 2; i <= num; i++) {

                sum = sum * i;

            }

            Console.WriteLine ("The Factorial of {0} is {1}", num, sum);

            Console.Write ( "Would you like to play again? (Y or N): " );

            string ans = Console.ReadLine();

            bool isValid = false;

            do

            {

                if( ans == "Y" || ans == "y" )  {

                    play = true;

                    isValid = true;

                    //break;

                }

                else if( ans == "N" || ans == "n" ) {

                    play = false;

                    isValid = true;

                    //break;

                }

                else

                {

                    Console.Write( "You have entered an invalid answer. Please choose from either Y or N: ");

                    ans = Console.ReadLine();

                    isValid = false;

                }

            }while(isValid == false);

        }

    }

}

}