proposition: Lemma hscI {Gamma ζ s t} : In s Gamma -> t = substitute ζ s -> hsc Gamma t.
proof: Proof. by move=> /hsc_var + ->. Qed.
imports: List Lia ssreflect ssrbool ssrfun Undecidability.HilbertCalculi.HSC Undecidability.HilbertCalculi.Util.HSCFacts Undecidability.PCP.PCP