You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 3-[4-[(5-ethylpyridin-2-yl)methyl]-6,6-dioxo-2,3,4a,5,7,7a-hexahydrothieno[3,4-b]pyrazin-1-yl]propanoic acid into molecular formula.
user
C17H25N3O4S
assistant