You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 1-[1-(3,4-difluorophenyl)ethyl]-3-ethyl-2-[4-(2-methylimidazol-1-yl)butyl]guanidine into molecular formula.
user
C19H27F2N5
assistant