proposition: Lemma Hall1 G : Hall G 1.
proof: Proof. by rewrite /Hall sub1G cards1 coprime1n. 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)