You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[2-(2,5-dimethoxyphenyl)acetyl]-9,10-dimethoxy-3,6,7,11b-tetrahydro-1H-pyrazino[2,1-a]isoquinolin-4-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C24H28N2O6
assistant