proposition: Lemma leU2r_le y t x z : x `&` t = \bot -> y `|` x <= t `|` z -> x <= z.
proof: Proof. by rewrite joinC [_ `|` z]joinC => /leU2l_le H /H. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)