You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
7-[(7-amino-7-carboxyheptanoyl)amino]-3-(carbamoyloxymethyl)-7-methoxy-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H26N4O9S
assistant