You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[6-[[methyl-(5-methylpyridin-2-yl)amino]methyl]imidazo[1,2-a]pyrazin-3-yl]benzamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H20N6O
assistant