using System;

public class Program

{

    public static void Main()

    {

Start: 

Console.WriteLine("What would you like to calculate the factorial of?"); 

        String x=Console.ReadLine(); 

        ulong y; 

        if(ulong.TryParse(x, out y))

        { ulong fact = 1;

         for (ulong i =1;i<=y;i++)

         {fact*=i;}

         Console.WriteLine(y+" != "+fact); 

         Console.WriteLine("Do you want to restart? Please Enter; Yes or No.");

         string answer = Console.ReadLine(); 

         if (answer=="Yes" || answer =="yes")

         { Console.Clear(); 

          goto Start;

                }

​

    }

}}