You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3S)-1-(2-fluorophenyl)-3-(4-methylpiperazine-1,4-diium-1-yl)pyrrolidine-2,5-dione The above is the IUPAC name of a molecule. Write its molecular formula.
user
C15H20FN3O2+2
assistant