You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Under IUPAC nomenclature, a molecule named 6-ethenyl-3-(4-methylsulfanylphenyl)-2-(propan-2-ylamino)pyrido[3,4-d]pyrimidin-4-one is given. What is its corresponding molecular formula?
user
C19H20N4OS
assistant