You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(5aS)-5-ethyl-N-[(4-methoxyphenyl)methyl]-11-oxo-6,7,8,9-tetrahydro-5aH-pyrido[2,1-b]quinazoline-3-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C23H27N3O3
assistant