You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[2-[(4-methylphenyl)sulfonylamino]-2-oxoethyl]-3-oxo-1,4-benzoxazine-6-carboxylic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H16N2O7S
assistant