You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl 2-[[5-(4-methoxyphenyl)-4-(4-methylphenyl)-1,2,4-triazol-3-yl]sulfanyl]propanoate is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H21N3O3S
assistant