You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4E)-4-[[4-[(2R)-butan-2-yl]oxyphenyl]methylidene]-5-methyl-2-(2,3,4,5,6-pentafluorophenyl)pyrazol-3-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H17F5N2O2
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