You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule N-[2-[4-[(3-fluoro-4-methoxyphenyl)methyl]piperazin-1-yl]-2-oxoethyl]-5-methylthiophene-2-carboxamide into molecular formula.
user
C20H24FN3O3S
assistant