You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name N-[2-[4-(3-fluorophenyl)piperazin-1-yl]-2-oxoethyl]-2-(3-methoxyphenyl)-2-oxoacetamide into its molecular formula.
user
C21H22FN3O4
assistant