You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name N-(4-chloro-1,3-benzothiazol-2-yl)-N-(3-imidazol-1-ylpropyl)-2-phenylacetamide;hydrochloride into its molecular formula.
user
C21H20Cl2N4OS
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