You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(4S)-4-(2-chlorophenyl)-4-methyl-2,5-dioxoimidazolidin-1-yl]-N-(2-fluorophenyl)acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H15ClFN3O3
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