You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
propan-2-yl N-[(2S)-7-cyano-4-(1,3-thiazol-2-ylmethyl)-2,3-dihydro-1H-cyclopenta[b]indol-2-yl]carbamate is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H20N4O2S
assistant