You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(7aS)-2-(1-cyclohexylpiperidin-4-yl)-7a-propyl-6,7-dihydro-5H-pyrrolo[1,2-c]imidazole-1,3-dione The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H33N3O2
assistant