You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 2-[(2S)-1-[(2S)-1-ethoxy-1-oxo-4-phenylbutan-2-yl]pyrrolidin-2-yl]acetic acid by IUPAC nomenclature, provide its molecular formula.
user
C18H25NO4
assistant