proposition: Lemma p'_elt_constt pi x : pi^'.-elt (x * (x.`_pi)^-1).
proof: Proof. by rewrite -{1}(consttC pi^' x) consttNK mulgK p_elt_constt. 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)