You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named [(2S,5R)-2-[2-(4-fluorophenyl)ethyl]-5-methylpyrrolidin-1-yl]-(2-methylphenyl)methanone by IUPAC nomenclature, provide its molecular formula.
user
C21H24FNO
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