You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-nitro-N-[2,2,2-trichloro-1-[[(1R,9R)-6-oxo-7,11-diazatricyclo[7.3.1.02,7]trideca-2,4-diene-11-carbothioyl]amino]ethyl]benzamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H20Cl3N5O4S
assistant