fact: Definition ltouch q := let: Gpoint x y := q in Grect (x - 1) (x + 1) (y - 1) (y + 1).
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(div choice order ssralg ssrnum ssrint intdiv) fourcolor(hypermap)