You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 5-methoxy-20-oxa-10-thia-3,12-diazapentacyclo[11.8.0.03,11.04,9.014,19]henicosa-1(13),4,6,8,11,14,16,18-octaene-2,21-dione by IUPAC nomenclature, provide its molecular formula.
user
C18H10N2O4S
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