You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(8S,8aS)-8-hydroxy-2-(4-nitrophenyl)-6,7,8,8a-tetrahydro-5H-imidazo[1,5-a]pyridine-1,3-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C13H13N3O5
assistant