You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
ethyl 2-[[2-[(5-pyridin-3-yl-1,3,4-oxadiazol-2-yl)sulfanyl]acetyl]amino]benzoate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H16N4O4S
assistant