proposition: Lemma ribbontb_stop_ltn : nth 0 inner stop < nth 0 outer stop.
proof: Proof. rewrite ltn_neqAle. have/includedP := incl => [[_ ->]]; rewrite andbT. have := mindropeq_non0. case H : mindropeq => [//|m] _ /=. by move: H => /eqP /(mindropeq_nthP _ (notin0_part partinn) (notin0_part partout)) []. Qed.
imports: HB(structures) mathcomp(all_ssreflect) tools sorted partition