You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the compound with this IUPAC name N-(3,4-dimethoxyphenyl)-2-(1-methyl-2,3,4,4a,5,7,8,8a-octahydro-1,6-naphthyridin-6-yl)propanamide ?
user
C20H31N3O3
assistant