You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[[4-(4-chlorophenyl)-5-(3-methoxyphenyl)-1,2,4-triazol-3-yl]sulfanylmethyl]pentanedinitrile is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H18ClN5OS
assistant