You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name 6-chloro-2-[[5-(4-methylpiperazin-1-yl)sulfonylpyridin-2-yl]sulfanylmethyl]-3H-quinazolin-4-one into its molecular formula.
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C19H20ClN5O3S2
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