You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(2R)-2-(2,4-dimethoxyphenyl)pyrrolidin-1-yl]-N-(2-fluoro-4-methylphenyl)acetamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H25FN2O3
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