You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (1R,3R,6S,7S,9R)-5-oxo-N-(4-phenoxyphenyl)-4-oxatricyclo[4.2.1.03,7]nonane-9-carboxamide into molecular formula.
user
C21H19NO4
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