You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(2-chloropyridin-4-yl)-N-(3-ethylphenyl)-4-(2-methylphenyl)-7,8-dihydro-5H-pyrido[4,3-d]pyrimidine-6-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C28H26ClN5O
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