And so these are two examples of diaryoisomers. And notice that these are both the Dtype molecule, the deisomer, because this green hydroxyl group found on the final stereogenic carbon, the farthest away from this aldehyme group, points to the right side. Remember, in the deisomers, the hydroxyl group found on the last theogenic carbon points to the right side. If this would have been the L, this would have pointed to the left side and we would have had this L erythro. So these are two examples of dirtyisomers. So, when two sugars have identical molecular formulas, have different arrangement of atoms and are not enantomers, they're not mere images, then they must be dieoisomers.