You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4S)-2-amino-4-(3-chloro-5-methoxy-4-prop-2-enoxyphenyl)-5-oxo-4,6,7,8-tetrahydrochromene-3-carbonitrile The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H19ClN2O4
assistant