proposition: Lemma p_eltJ pi x y : pi.-elt (x ^ y) = pi.-elt x.
proof: Proof. by congr pnat; rewrite orderJ. 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)