proposition: Lemma genV A : <<A^-1>> = <<A>>.
proof: Proof. apply/eqP; rewrite eqEsubset !gen_subG -!(invSg _ <<_>>) invgK. by rewrite !invGid !subset_gen. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)