You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(1R,2S,6R,7S)-4-[(Z)-(3,4-dimethoxyphenyl)methylideneamino]spiro[4-azatricyclo[5.2.1.02,6]dec-8-ene-10,1'-cyclopropane]-3,5-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H20N2O4
assistant