proposition: Lemma F_surjective : forall y, exists x, F x y.
proof: Proof. Proof using M2_correct. apply (induction M2 M2_correct). - exists O1. exact F_O. - intros y [x IH]. exists (S1 x). now apply F_S. Qed.
imports: PeanoNat Lia Vector Undecidability.SOL(SOL PA2) Undecidability.Shared.Libs.PSL(Vectors) Undecidability.SOL.Util(Syntax Subst Tarski PA2_facts)