You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(5E)-5-chromeno[2,3-c]pyridin-5-ylidene-2-methylchromeno[2,3-c]pyridin-2-ium is the IUPAC name of a molecule. Please give its molecular formula.
user
C25H17N2O2+
assistant