You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[2-(1,3-benzothiazol-2-yl)pyrrolidine-1-carbonyl]-N-ethyl-4-methylbenzenesulfonamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H23N3O3S2
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