You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 9H-fluoren-9-ylmethyl (2S,4S)-4-[[(2S)-2-amino-3-[(2S)-2-cyanopyrrolidin-1-yl]-3-oxopropyl]amino]-2-formylpyrrolidine-1-carboxylate by IUPAC nomenclature, provide its molecular formula.
user
C28H31N5O4
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