You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(2,7-dimethylindazol-5-yl)-9-methyl-7-piperidin-4-ylpyrazino[1,2-a]pyrimidin-4-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C22H24N6O
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