While this initial analysis provided a metric for the transformations that would give the greatest proportion of unknown products relative to the total number of products generated, it cannot be used alone to judge the value of each skeletal edit. Specifically, because some transformations may be accomplished by inserting, removing, or changing the identity of the same type of atom at different positions in the ring, more than one product is generated for each starting molecule for some transformations. This over-emphasizes the potential benefit of transformations that generate more than one product molecule for each starting compound. For example, a 2-substituted pyridine can be converted into two different pyrimidines by exchanging either C3 or C5 for a nitrogen atom. Additionally, ring contraction of pyridines to pyrroles could be accomplished by removing any one of the five carbon atoms in the pyridine ring.