You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2R)-2-(4-ethyl-7-methyl-2-oxochromen-5-yl)oxy-N-(pyridin-4-ylmethyl)propanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H22N2O4
assistant