You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
7-[3-(4-chlorophenyl)-1,2,4-oxadiazol-5-yl]-3-pentyl-4a,5,6,7,8,8a-hexahydro-1H-quinazoline-2,4-dione The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H25ClN4O3
assistant