You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[(4R)-4-ethyl-2,5-dioxo-4-phenylimidazolidin-1-yl]-3-(3-fluoro-4-methylphenyl)thiourea is the IUPAC name of a molecule. Please give its molecular formula.
user
C19H19FN4O2S
assistant