You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[5-(4,6-diphenyl-1,3,5-triazin-2-yl)spiro[benzo[c]fluorene-7,9'-thioxanthene]-2'-yl]benzonitrile is the IUPAC name of a molecule. Please give its molecular formula.
user
C51H30N4S
assistant