You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[[1-(2-methoxyethyl)cyclopentyl]methyl]-2-methyl-3-[4-(2-methyl-6-oxopyridin-1-yl)butyl]guanidine is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H36N4O2
assistant