You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[1-[3-[(dimethylamino)methyl]-3,5-dihydro-2H-1,4-benzoxazepin-4-yl]-1-oxopropan-2-yl]-2-methoxyacetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H27N3O4
assistant