You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[[2-[2-(4-nitrophenyl)-2-oxoethyl]sulfanylpyrimidin-4-yl]amino]benzenesulfonamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H15N5O5S2
assistant