You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 4-[2-[5-(5-methylpyrimidin-4-yl)-1,3,3a,4,6,6a-hexahydropyrrolo[3,4-c]pyrrol-2-yl]ethyl]-1,4-oxazepan-5-one into molecular formula.
user
C18H27N5O2
assistant