You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(4a-methyl-3-oxo-2,4,5,6-tetrahydrothieno[3,2-h]cinnolin-7-yl)acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C13H15N3O2S
assistant