You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named phenyl 3-amino-6-methyl-7,8-dihydro-5H-thieno[2,3-b][1,6]naphthyridine-2-carboxylate is given. What is its corresponding molecular formula?
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C18H17N3O2S
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