You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[[3-(3-chlorophenyl)-1,2,4-oxadiazol-5-yl]methyl]-3-[3-(2-oxopyrrolidin-1-yl)phenyl]thiourea The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H18ClN5O2S
assistant