You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name ethyl 2-[(7-oxo-3,6-diphenyl-2-sulfanylidene-[1,3]thiazolo[4,5-d]pyrimidin-5-yl)sulfanyl]acetate into its molecular formula.
user
C21H17N3O3S3
assistant