You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule identified by 1-(4-methylpiperazin-1-yl)-2-[4-[(3-methyl-2H-pyrazolo[3,4-b]pyridin-5-yl)methylamino]phenyl]ethanone ?
user
C21H26N6O
assistant