proposition: Fact btrm_inv u s t : u ⋷ s⪧t <-> u = s \/ u ⋷ t.
proof: Proof. split. + inversion 1; auto. + intros [ <- | ]; constructor; auto. Qed.
imports: List Arith Lia Max Wellfounded Setoid Eqdep_dec Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_list utils_decidable finite seteq) Undecidability.Shared.Libs.DLW.Vec(pos) Undecidability.Shared.Libs.DLW.Wf(wf_finite wf_chains) Undecidability.FOL.TRAKHTENBROT(notations fol_ops)