using System;

public class Program

{

    public static void Main()

    {

        start:

        Console.Clear();

        Console.WriteLine("Type in a positive integer and press enter");

        start2:

        string number = Console.ReadLine();

        ulong fact = 1;

        if(ulong.TryParse(number, out fact))

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

         goto start2;

        }

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

        {fact *=i;}

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

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

        string choice = Console.ReadLine();

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

        goto start;

​

    }

}