You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[2-(1H-benzimidazol-2-yl)ethyl]-3-ethyl-2-[2-[4-(trifluoromethyl)-1,3-thiazol-2-yl]ethyl]guanidine is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H21F3N6S
assistant