Hello Everyone!

The link to the question

https://atcoder.jp/contests/abc172/tasks/abc172_f

The approach I am unable to understand.

https://codeforces.net/blog/entry/79438

I am finding it difficult to how is the author deciding what bits to set in x on basis of S. Mainly the 3rd and 4th paragraph of the solution, I am unable to grasp.

It would be really helpful if someone who was able to understand the approach can describe in his own words.

Thank you