You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule ethyl 7,7-dimethyl-3-phenyl-2,5-bis(sulfanylidene)-1,6-dihydroimidazo[1,5-b][1,2,4]triazole-7a-carboxylate .
user
C15H18N4O2S2
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