You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl (1R,9S,13S)-9-ethyl-4-methoxy-10-phenyl-11-sulfanylidene-8-oxa-10,12-diazatricyclo[7.3.1.02,7]trideca-2(7),3,5-triene-13-carboxylate is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H22N2O4S
assistant