You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named [(2S)-1-[(3-fluorophenyl)methyl-methylamino]-1-oxopropan-2-yl] 1-benzothiophene-2-carboxylate by IUPAC nomenclature, provide its molecular formula.
user
C20H18FNO3S
assistant