fact: Definition popqa r := match r with | Pr56 => Pr55 | Pr57 => Pr56 | Pr58 => Pr57 | Pr67 => Pr66 | Pr68 => Pr67 | Pr78 => Pr77 | _ => Pr99 end.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry part quiz quiztree)