You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Under IUPAC nomenclature, a molecule named 4-(2,3,3a,4-tetrahydro-1H-pyrrolo[1,2-a]quinoxalin-5-yl)-4-oxo-N-propylbutanamide is given. What is its corresponding molecular formula?
user
C18H25N3O2
assistant