You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
12,18-dibromo-5',5'-dimethylspiro[4,26-dioxaheptacyclo[14.11.0.02,14.03,11.05,10.019,27.020,25]heptacosa-1(27),2,5,7,9,11,13,16,18,20,22,24-dodecaene-15,10'-benzo[b][1]benzosiline] The above is the IUPAC name of a molecule. Write its molecular formula.
user
C39H24Br2O2Si
assistant