You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[7-(3,4-dimethoxyphenyl)-6,7-dihydro-5H-pyrrolo[1,2-c]imidazol-5-yl]-3-fluorobenzonitrile The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H18FN3O2
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