You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-(2,6-dichlorophenyl)-7-[4-(2-hydroxyethyl)anilino]-1-methyl-4H-pyrimido[4,5-d]pyrimidin-2-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H19Cl2N5O2
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