You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(4-fluoro-3-methylphenyl)-6-methyl-4-[(3R)-3-methylpiperidin-1-yl]thieno[2,3-d]pyrimidine-5-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H23FN4OS
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