You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[4-[(E)-2-cyano-3-(3-methoxypropylamino)-3-oxoprop-1-enyl]-2-ethoxy-6-iodophenoxy]acetic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H21IN2O6
assistant