You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(3S,5S)-5-cyano-1-[(2S,3S)-2-[9H-fluoren-1-yl(methoxycarbonyl)amino]-3-methylpentanoyl]pyrrolidin-3-yl] acetate is the IUPAC name of a molecule. Please give its molecular formula.
user
C28H31N3O5
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