You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl 5-[(2S)-2-[(2R)-2-(2,4-dichlorophenoxy)propanoyl]oxypropanoyl]-2,4-dimethyl-1H-pyrrole-3-carboxylate is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H21Cl2NO6
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