The ZINC database used for training is a database for virtual screening, and contains over 750 million molecules. Approximately 250,000 molecules, which are commonly used in molecular generative models, were used for training. This dataset is the same as that used in ChemTS, and is publicly available at . 22,234 fragments obtained by applying the procedure described in the Methods section to each molecule were used for training. An example of the fragments used for training is shown in Fig. .