You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-(1-benzofuran-2-yl)-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b]azepin-2-amine is the IUPAC name of a molecule. Please give its molecular formula.
user
C16H16N4O
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