You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[1-(4-aminophenyl)-3-pyridin-3-yl-4,5-dihydropyrazolo[4,3-g][1,3]benzothiazol-7-yl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H18N6OS
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