however maths theory is limited ,but idea is same in most problems,if you are good in maths mostly number theory then cp is easy for u else u would find cp difficult

Whenever a problem is with numbers, but the order of the numbers is not actually important,I think it is easy to look at them as points in a line. If you look at this problem that way, the operation just tells you the distance to that point. Then the 40 operations can give you a hint that it has to do something with O(logN). So if you are imagining the points in a line, you can think "maybe I can think of the points being in range [L,R]" and think how can you cut that range length in half.