using System;

public class Program

{

    public static void Main()

    {

        start:

        Console.Clear();

        Console.WriteLine("Please Enter a Positive Integer:");

        oops:

        string sans = Console.ReadLine();                                         ;

        ulong ans;

        if (ulong.TryParse(sans, out ans));                                                 );

        {

            if (ans >= 66)

            {

                Console.WriteLine("Please enter a number less than 66");

                goto oops;

            }

            else

            {

                ulong fact = 1;

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

                {

                    fact *= i;

                }

​

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

            }

            {

        else

        {

            Console.WriteLine("Please Enter A POSITIVE NUMBER!");

            goto oops;

        }

​

        Console.WriteLine("Would you like to run the program again? y/n");

        string choice = Console.ReadLine();

        if (choice == "y" ||choice == "Y");

            goto start;

​

​

    }

}