You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4Z)-4-[[3-bromo-4-[(2S)-butan-2-yl]oxy-5-nitrophenyl]methylidene]-1-phenylpyrazolidine-3,5-dione The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H18BrN3O5
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