You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name N-[(2S)-butan-2-yl]-N-[(3S)-1,1-dioxothiolan-3-yl]-2-[4-(2-methoxyphenyl)piperazin-1-yl]acetamide into its molecular formula.
user
C21H33N3O4S
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