You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N,N-diethyl-2-(2,3,4,6,7,8,9,10-octahydropyrimido[1,2-a]azepin-8-yl)ethanamine is the IUPAC name of a molecule. Please give its molecular formula.
user
C15H29N3
assistant