You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[3-(4-fluorophenyl)-1,2,4-oxadiazol-5-yl]-1-[4-(thiophen-3-ylmethyl)piperazin-1-yl]propan-1-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H21FN4O2S
assistant