You can find the problem there 1930F - Максимизируйте разницу.
Before you continue the reading, this is my first blog, I don't know how to write mathematical formulas with codeforces, as for example maximum over a set. If any advice for this it will be helpful.
Problem statement
Given an array b of m non-negative integers, we must calculate f(b) as the maximum value of max(bi|x)−min(bi|x) over all possible non-negative integers x.
And as hints, the editorial mention :
For an array b consiting of m non-negative integers, f(b)=max(max(bi|bp)−min(bi|bp))
f(b) is the maximum value of bi ∧ ~ bj over all pairs
If you have any solution feel free to comment on it. Thanks!!!