You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
5-[6-[(3R)-1-acetylpiperidin-3-yl]-2-methylpyrimidin-4-yl]pyridine-3-carboxylic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H20N4O3
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