You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule 2-[3-(2-acetamidoethyl)-5-oxo-1-phenyl-2-sulfanylideneimidazolidin-4-yl]-N-(4-fluorophenyl)acetamide .
user
C21H21FN4O3S
assistant