You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[2-(1,3-benzothiazol-2-yl)ethyl]-3-(1,4-dioxo-3H-phthalazin-2-yl)propanamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H18N4O3S
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