fact: Definition drule18 := Part $ 6 $[5] 5 $[5] 7 $ 6+ $ * $ * $ 5 $.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) mathcomp(bigop order ssralg ssrnum ssrint) fourcolor(hypermap geometry part)