proposition: Lemma gotos_igotos {n X Y} : In (n, X, Y) gotos -> exists i, In (i, (n, X, Y)) igotos.
proof: Proof. move /(In_nth_error gotos) => [i /nth_error_Some_In_combineP ?]. by exists i. Qed.
imports: Relation_Operators Operators_Properties Lia PeanoNat List Undecidability.StackMachines.Reductions.CM1_HALT_to_SMNdl_UB.SMX_facts Undecidability.StackMachines.Util(Nat_facts List_facts) ssreflect ssrbool ssrfun