fact: Definition prange_lo k := match k with | 5 => Pr55 | 6 => Pr56 | 7 => Pr57 | 8 => Pr58 | _ => Pr59 end.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap color geometry)