You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4E)-4-[4-(4-bromophenyl)-3H-1,3-thiazol-2-ylidene]-1-(4-ethoxyphenyl)-5-iminopyrrolidin-2-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H18BrN3O2S
assistant