proposition: Lemma oddSg G H : H \subset G -> odd #|G| -> odd #|H|.
proof: Proof. by rewrite !odd_2'nat; apply: pgroupS. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(fintype bigop finset prime fingroup morphism) mathcomp(gfunctor automorphism quotient action gproduct) mathcomp(cyclic)