The problem calls digits in integer number "special" if they are "local maximum" (2 points) or "minimum" (1 point) among neighbors. And asks to calculate points for all numbers in a given range. It won't be hard for bruteforce if ranges are not on order 10^18 :) Thus it is most probable some kind of DP but I'm completely out of ideas how exactly to approach it. If someone can give such a subtle hint as direct me without spoiling the solution, it would be great!