You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(5-phenyl-1,3,4-oxadiazol-2-yl)methyl 3-(3-methyl-4-oxoquinazolin-2-yl)propanoate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H18N4O4
assistant