You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-ethyl-3-[[2-(ethylcarbamothioylhydrazinylidene)-1-(4-nitrophenyl)-2-phenylethylidene]amino]thiourea is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H23N7O2S2
assistant