You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 1-methyl-N-[2-[4-(1-methylcyclobutanecarbonyl)piperazin-1-yl]sulfonylethyl]cyclobutane-1-carboxamide into molecular formula.
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C18H31N3O4S
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