You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[3-[(4S)-2-amino-1,4-dimethyl-6-oxo-5H-pyrimidin-4-yl]phenyl]-2-methylbenzimidazole-4-carbonitrile The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H20N6O
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