You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name 2-(7-chloro-5-naphthalen-1-yl-2-oxo-1,5-dihydro-4,1-benzothiazepin-3-yl)acetic acid into its molecular formula.
user
C21H16ClNO3S
assistant