You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[(4R)-2,5-dioxo-1-[(1R)-1-phenylethyl]imidazolidin-4-yl]-N-(pyridin-2-ylmethyl)propanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H22N4O3
assistant