proposition: Lemma leIx2 x y z : (y <= x) || (z <= x) -> y `&` z <= x.
proof: Proof. by case/orP => [/leIxl|/leIxr]. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)