You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
7-chloro-6-[4-(dimethylamino)phenyl]-4-hydroxy-3-(3-methyl-1,2-oxazol-5-yl)-1H-quinolin-2-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H18ClN3O3
assistant