You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(4aS,8aS)-4a-hydroxy-1,3,4,5,6,7,8,8a-octahydroisoquinolin-2-yl]-(4-nitrophenyl)methanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C16H20N2O4
assistant