You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(2,4-difluorophenyl)-5-(pyridin-2-ylmethyl)-3,4,6,7-tetrahydroimidazo[4,5-c]pyridine is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H16F2N4
assistant