You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 6-(1H-imidazol-2-yl)-2-[4-(1H-imidazol-2-yl)phenyl]-1H-indole;dihydrochloride into molecular formula.
user
C20H17Cl2N5
assistant