You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(3-amino-9H-fluoren-2-yl)-N-[4-(furan-2-yl)-6-sulfanylidene-1,3-thiazin-2-yl]nitramide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H14N4O3S2
assistant