You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[4-[ethyl-[3-(2-methylpropyl)pyridin-2-yl]amino]piperidin-1-yl]-(1H-pyrrol-2-yl)methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H30N4O
assistant