You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4R)-4-[4-[1-(5-chloropyrimidin-2-yl)azetidin-3-yl]oxyphenyl]pentan-2-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H20ClN3O2
assistant