You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-(4-chlorophenyl)-N-(4-methyl-2-oxo-3,4,4a,5,6,7,8,8a-octahydro-1H-quinolin-7-yl)-4-oxobutanamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H25ClN2O3
assistant