You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-(3,4-dimethylphenyl)-4-ethylsulfanyl-1-[(2-fluorophenyl)methyl]pyrrole-2,5-dione The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H20FNO2S
assistant