You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(E)-2-(4-chlorophenyl)ethenyl]-5-[4-(furan-2-carbonyl)piperazin-1-yl]-1,3-oxazole-4-carbonitrile is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H17ClN4O3
assistant