proposition: Lemma neq_ccw d : (ccw d == d) = false.
proof: Proof. by apply/eqP=> /(congr1 oddg); rewrite -ccw_odd; case: oddgP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(div choice order ssralg ssrnum ssrint intdiv) fourcolor(hypermap)