using System;

public class Program

{

    public static void Main()

    {

        start:

        Console.WriteLine("Please enter a number that you would like to calculate the factorial of.");

        ulong input = ulong.Parse(Console.ReadLine());

                if(input >= 66)

        {Console.WriteLine("Please enter a smaller number.");

         Console.ReadLine();

         Console.Clear();

            goto start; }

        ulong fact =1;

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

        {fact *=i;}

        Console.WriteLine("The factorial of " +input+ " is = " + fact);

        Console.WriteLine("Would you like to restart the program?");

        string ans = Console.ReadLine();

            if (ans == "yes")

            { Console.Clear();

            goto start; }

        else

        { Console.Clear();

         Console.WriteLine("Hope you enjoyed!"); }

}

}