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 7-(2-methoxyacetyl)-1-(pyridin-3-ylmethyl)-5,6,8,9-tetrahydropyrido[2,3-d]azepin-2-one is given. What is its corresponding molecular formula?
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C18H21N3O3
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