You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2R)-2-(2,3-dihydroindol-1-yl)-1-[(3S)-3-(1-methylpyrrol-2-yl)morpholin-4-yl]propan-1-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H25N3O2
assistant