You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(2S)-4-[(2-chloro-3,4-dimethoxyphenyl)methyl]-1-(3-methylbutyl)piperazin-2-yl]ethanol is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H33ClN2O3
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