You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
ethyl 4-[3-[(3-cyano-6,7-dihydro-5H-cyclopenta[b]pyridin-2-yl)sulfanyl]propanoylamino]benzoate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H21N3O3S
assistant