You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[ethyl-[1-[2-(2-methyl-4-nitroanilino)-2-oxoethyl]piperidin-4-yl]amino]acetic acid The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H26N4O5
assistant