You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(4-methylphenyl)methyl]-5-(quinolin-4-ylsulfanylmethyl)-1,3,4-thiadiazole-2-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H18N4OS2
assistant