isISBN13 = function(n)
	n = n.replace("-","").replace(" ","")
	s = 0
	for i in range(0, n.len-1,2)
		s += n[i].val
	end for
	for i in range(1, n.len-1,2)
		s += n[i].val * 3
	end for
	return not (s % 10)
end function

testValues = "978-0596528126 978-0596528120 978-1788399081 978-1788399083".split(" ")
for val in testValues
	print val + " " + ["bad", "good"][isISBN13(val)]
end for