You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 4-[[(3R)-3-butyl-4-[(2-methylpropan-2-yl)oxycarbonyl]piperazin-1-yl]methyl]benzoic acid into molecular formula.
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C21H32N2O4
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