proposition: Lemma dvdn_cardMg G H : #|G * H| %| #|G| * #|H|.
proof: Proof. by rewrite mul_cardG dvdn_mulr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)