You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Under IUPAC nomenclature, a molecule named [1-[(2-chlorophenyl)methyl]pyrazol-4-yl]-[4-(3-fluorophenyl)sulfonylpiperazin-1-yl]methanone is given. What is its corresponding molecular formula?
user
C21H20ClFN4O3S
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