You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
dimethyl 1-(2-chloropyridin-4-yl)-1-formyl-6-hydroxy-7-methoxynaphthalene-2,2-dicarboxylate is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H18ClNO7
assistant