You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
O-[(4-nitrophenyl)methyl] (6R)-7-amino-3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carbothioate is the IUPAC name of a molecule. Please give its molecular formula.
user
C15H15N3O4S2
assistant