You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(2-chlorophenyl)-4-[3-(3,4-dimethoxyphenyl)-1,2,4-oxadiazol-5-yl]butanamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H20ClN3O4
assistant