proposition: Lemma mulG_sub K H A : K * H = A -> K \subset A /\ H \subset A.
proof: Proof. by move <-; rewrite mulG_subl mulG_subr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)