You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3R)-N-ethyl-1-oxo-N-[2-oxo-2-(thiophen-2-ylmethylamino)ethyl]-3,4-dihydroisochromene-3-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C19H20N2O4S
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