Ask HN: What are the most important challenges?

Say you had no need to make a living - imagine you win the lottery or something like that. You don't get to have millions but you don't _need_ to work.

Now imagine that you still _want_ to work but now you can select to work on whatever you want.

Lastly, say that you would want to maximize your impact on helping solving most pressing problems for humanity now.

What would it be? What would you work on? Just curious to see what strikes as a priority.