proposition: Lemma lexUr x y z : x <= z -> x <= y `|` z.
proof: Proof. exact: (@leIxr _ L^d). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)