fact: Definition cdrv n (s t : obstring n) := match s, t with | Some (exist _ s _), Some (exist _ t _) => derivable R s t | _, _ => False end.
imports: Lia Arith Undecidability.PCP.PCP Undecidability.PCP.Util.PCP_facts Undecidability.Synthetic.DecidabilityFacts Undecidability(FOL.Utils.FullSyntax) Undecidability(FOL.FSAT) Undecidability.Shared.ListAutomation