You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(4-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-d]azepin-3-yl)-N-(2-quinolin-8-ylethyl)acetamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H23N5O2
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