You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[2-oxo-2-[[(1R)-1-phenylethyl]amino]ethyl] 4-oxo-3,5-dihydro-2H-1,5-benzothiazepine-7-carboxylate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H20N2O4S
assistant