You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(15S,19S)-16,18-dioxo-17-azapentacyclo[6.6.5.02,7.09,14.015,19]nonadeca-2,4,6,9,11,13-hexaen-17-yl]ethyl 2-phenylacetate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C28H23NO4
assistant