proposition: Lemma nat_not_neg x : ~(x < 0).
proof: Proof. apply le_not_lt_flip, nat_nonneg. Qed.
imports: HoTT.Types.Sigma HoTT.Classes.theory.naturals HoTT.Classes.interfaces.abstract_algebra HoTT.Classes.interfaces.orders HoTT.Classes.theory.rings HoTT.Classes.orders.rings HoTT.Classes.implementations.peano_naturals HoTT.Classes.orders.nat_int