proposition: Lemma transparent_encode_pair {ζ s t} : ζ 0 = var 0 -> substitute ζ (encode_pair s t) = encode_pair (substitute ζ s) (substitute ζ t).
proof: Proof. by move=> /= ->. Qed.
imports: List Lia ssreflect ssrbool ssrfun Undecidability.HilbertCalculi.HSC Undecidability.HilbertCalculi.Util.HSCFacts Undecidability.PCP.PCP