You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(3,4-dichlorophenyl)-4-(4-imidazol-1-ylphenyl)-N-propyl-1,3-thiazol-2-amine The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H18Cl2N4S
assistant