You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(3,4-dichlorophenyl)-4-[[4-(dimethylamino)-3-nitrophenyl]methylidene]-5-methylpyrazol-3-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C19H16Cl2N4O3
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