fact: Definition dscore x : int := 60%:Z - (10 * arity x)%:Z + \sum_(y in cface x) dscore2 y.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) mathcomp(bigop order ssralg ssrnum ssrint) fourcolor(hypermap geometry part)