fact: Definition solving (v w: list bool) P n := exists A, (incl A ((v, w) :: P)) /\ exists ζ, der (Γ v w P) n (substitute ζ (encode_pair (encode_word (v ++ tau1 A)) (encode_word (w ++ tau2 A)))).
imports: List Lia ssreflect ssrbool ssrfun Undecidability.HilbertCalculi.HSC Undecidability.HilbertCalculi.Util.HSCFacts Undecidability.PCP.PCP