fact: Definition red_popl_fan3r pl pr := match pl with | Pcons8 h f1 f2 f3 _ => red_pcons (fun r => Pcons8 h f1 f2 r) f3 pr | _ => true end.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry part quiz quiztree)