proposition: Lemma p_eltV pi x : pi.-elt x^-1 = pi.-elt x.
proof: Proof. by rewrite /p_elt orderV. 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)