You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(1-methylimidazol-2-yl)-N-[1-methyl-4-(pyridin-2-ylmethyl)piperidin-4-yl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H25N5O
assistant