You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule N-[4-(4-ethylphenyl)-1,3-thiazol-2-yl]-2-(6-fluoro-4-oxoquinazolin-3-yl)acetamide into molecular formula.
user
C21H17FN4O2S
assistant