You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-ethyl-13-(2-methoxyethyl)-9-thiophen-2-ylsulfonyl-3,9,13-triazadispiro[4.0.56.35]tetradecan-4-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H31N3O4S2
assistant