fact: Definition maybe_reachable (M: SMX) (n: nat) (X Y: Config) : Prop := reachable_n M n X Y \/ (exists Z, reachable_n M n X Z /\ terminal M Z).
imports: List Lia Relation_Operators Undecidability.StackMachines.Util(Nat_facts List_facts) Undecidability.StackMachines.Reductions.CM1_HALT_to_SMNdl_UB.SMX ssreflect ssrbool ssrfun