You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
6,6-difluoro-9-[(4-fluorophenyl)methyl]-2-pyrazin-2-yl-2,9-diazaspiro[4.5]decane The above is the IUPAC name of a molecule. Write its molecular formula.
user
C19H21F3N4
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