You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[2-[3-(3,4-dihydro-1H-isoquinolin-2-yl)azetidin-1-yl]-2-oxoethyl]-5,6-dimethylpyrimidin-4-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H24N4O2
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