mrc:<prolog>prolog
Prolog-10  version 3

| ?- [col1].

col1 consulted   940 words      0.42 sec.

yes
| ?- test.
countries
[←42,←43,←44,←45,←46,←47]

unarranged goals
[next(←42,←43),next(←42,←44),next(←42,←46),next(←42,←47),next(←43,←44),next(←43,←45),next(←43,←46),next(←43,←47),next(←44,←45),next(←44,←47),next(←46,←47)]

arranged goals
[[next(←42,←46),next(←43,←45),next(←43,←46),next(←44,←45),next(←46,←47)],[next(←42,←43),next(←42,←44),next(←42,←47),next(←43,←44),next(←43,←47),next(←44,←47)],[]]

solution
[y,b,g,y,g,r]

yes
| ?-