proposition: Lemma constt1P pi x : reflect (x.`_pi = 1) (pi^'.-elt x).
proof: Proof. rewrite -{2}[x]expg1 p_elt_exp -order_constt consttNK order_dvdn expg1. exact: eqP. 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)