You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the compound with this IUPAC name 2-chloro-3-[[ethyl-[(5-propyl-1,2,4-oxadiazol-3-yl)methyl]amino]methyl]-9-methylpyrido[1,2-a]pyrimidin-4-one ?
user
C18H22ClN5O2
assistant