You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[4-[(2-azabicyclo[2.2.1]heptan-4-ylamino)methyl]-3-oxo-1H-isoindol-2-yl]piperidine-2,6-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H24N4O3
assistant