You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 4-[4-[4-chloro-3-(trifluoromethyl)phenyl]sulfonylpiperazin-1-yl]butan-2-one by IUPAC nomenclature, provide its molecular formula.
user
C15H18ClF3N2O3S
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