You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule N-[7-(ethylamino)-5-(3-methylphenyl)sulfonyl-7,8-dihydro-6H-1,5-naphthyridin-3-yl]formamide into molecular formula.
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C18H22N4O3S
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