You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(2S)-1-(3-chloro-4-fluoroanilino)-1-oxopropan-2-yl] 2-[(1R,2R,3S)-3-methyl-2-(nitromethyl)-5-oxocyclopentyl]acetate The above is the IUPAC name of a molecule. Write its molecular formula.
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C18H20ClFN2O6
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