You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N,N-dimethyl-4-[2-(3-methylbenzo[g][1,3]benzoselenazol-3-ium-2-yl)ethenyl]aniline is the IUPAC name of a molecule. Please give its molecular formula.
user
C22H21N2Se+
assistant