You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(3Z)-3-(aminomethylidene)-4-ethyliminocyclohexyl]-8-(2-methylpyridin-3-yl)-[1,2,4]triazolo[1,5-a]pyridin-2-amine is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H25N7
assistant