You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule identified by 7-methyl-2-[(5-methyl-1,3,4-oxadiazol-2-yl)methylsulfanyl]-3-prop-2-enyl-5,6,7,8-tetrahydro-[1]benzothiolo[2,3-d]pyrimidin-4-one ?
user
C18H20N4O2S2
assistant