proposition: Lemma iff_intro {A} (P Q : A -> Prop) : (forall a, P a <-> Q a) -> (forall a, P a) <-> (forall a, Q a).
proof: Proof. firstorder. Qed.
imports: Coq(ZArith Znumtheory Lia Psatz List Bool) Coqtail(Ztools Zeqm Zlittle_fermat Zpow Zprime)