You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Under IUPAC nomenclature, a molecule named 2-[(2-amino-6-oxo-1,7-dihydropurin-8-yl)sulfanyl]-N-(4-piperidin-1-ylsulfonylphenyl)acetamide is given. What is its corresponding molecular formula?
user
C18H21N7O4S2
assistant