fact: Definition refine_rect r := let: Grect x0 x1 y0 y1 := r in Grect (x0 *+ 2) (x1 *+ 2) (y0 *+ 2) (y1 *+ 2).
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(div choice order ssralg ssrnum ssrint intdiv) fourcolor(hypermap)