You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(4-chlorophenyl)-5-methyl-3-(3-nitrophenyl)-3a,6a-dihydro-3H-pyrrolo[3,4-d][1,2]oxazole-4,6-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H14ClN3O5
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