color(map_eu, [[belgium, yellow], [netherlands, green], [luxemburg, green], [france, blue], [germany, red], [italy, red], [denmark, green], [ireland, red], [greece, red], [spain, green], [portugal, red], [austria, yellow], [sweden, green], [finland, red], [cyprus, red], [malta, red], [poland, blue], [hungary, blue], [czech_republic, green], [slovakia, red], [slovenia, green], [estonia, red], [latvia, green], [lithuania, red], [bulgaria, green], [romania, red], [croatia, red]]).
status(map_eu, valid_four_colour_assignment).
reason(map_eu, "no neighbouring countries share a colour").