proposition: Lemma leBC x y : x `\` y <= ~` y.
proof: Proof. by rewrite leBLR joinxC lex1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)