You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[[4-[[(3R,5S)-3,5-dimethylpiperidin-1-yl]methyl]phenyl]methyl]-1-methyl-6-oxopyridazine-3-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H28N4O2
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