You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule N-(2,4-difluorophenyl)-N-[2-[4-(2-methoxyphenyl)piperazin-1-yl]-2-oxoethyl]methanesulfonamide into molecular formula.
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C20H23F2N3O4S
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