You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-ethyl-3,5,5a,6,7,8,9,9a-octahydro-2H-pyrido[4,3-e][1,4]oxazepine by IUPAC nomenclature, provide its molecular formula.
user
C10H20N2O
assistant