You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[5-methyl-6-(2-morpholin-4-ylethyl)thieno[2,3-b]pyrrol-2-yl]-(6-methylpyridin-2-yl)methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H23N3O2S
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