You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(6-amino-5-ethylpyridin-3-yl)-2-[(2R,5S)-2-(3,5-dichlorophenyl)-5-methylpiperidin-1-yl]-2-oxoacetamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H24Cl2N4O2
assistant