You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2S)-1'-benzyl-3-(3-fluoro-4-methylphenyl)spiro[1,3-thiazinane-2,3'-indole]-2',4-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C25H21FN2O2S
assistant