You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[3',6'-bis(diethylamino)-3-oxospiro[isoindole-1,9'-xanthene]-2-yl]ethyl methanesulfonate is the IUPAC name of a molecule. Please give its molecular formula.
user
C31H37N3O5S
assistant