Namespace System.Collections.Generic
Module VBModule
  Sub Main()
    console.writeline("Enter ISBN:")
    Dim isbn As String = console.readline()
    isbn = isbn.Replace("-","")
    Dim length As Integer = len(isbn)
    Dim counter As Integer = 0
    Dim isbn_list As New List (Of Integer)
    Dim looping As Boolean
    Do Until looping = False
    	Dim num As Integer = Convert.toInt32(isbn.Substring(counter,counter+1))
    	isbn_list.Add(num)
    	counter += 1
    	If counter = Length-1 Then
    		looping = False
    	End If
    Loop
    console.writeline(isbn_list(1))
    counter = 0
    Dim sum As Integer = 0 'Haha... Dim Sum
    Do Until counter = length - 1
    	If counter Mod 2 = 0 Then
    		sum += isbn_list.Item(counter)
    	Else
    		sum += (isbn_list(counter))* 3
    	End If
    Loop
    Dim check As Integer = sum Mod 10
    If check = isbn_list(length) Then
    	console.writeline("You entered a valid code.")
    Else
    	console.writeline("You entered an invalid code.")
    End If
  End Sub
End Module

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