You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name N-[(2S)-2-chloro-9-[(2R,3R,4R,5R)-3,4-dihydroxy-5-(hydroxymethyl)-3-methyloxolan-2-yl]-6-oxo-1,8-dihydropurin-2-yl]benzamide into its molecular formula.
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C18H20ClN5O6
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