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 2-butan-2-yl-6-(3-hydroxyphenyl)-9-methyl-7,8-dihydropyrimido[4,5-e][1,4]diazepin-5-one is given. What is its corresponding molecular formula?
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C18H22N4O2
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