You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule 2-methyl-6-[1-(2-phenylethyl)-6,7-dihydro-4H-imidazo[4,5-c]pyridin-5-yl]pyridine-4-carbonitrile .
user
C21H21N5
assistant