You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-(2,4-dimethylphenyl)-6-(4,6-dimethylpyrimidin-2-yl)-4-methylpyrazolo[3,4-d]pyridazin-7-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H20N6O
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