And that time spent writing a small paper in one's native language would be better spent trying to make the code speak for itself. Maybe get some help, pair up and tackle the complexity. And when both/all involved is like, we can't make this any clearer and it's still confusing af. _Then_ it's time to write that lengthy comment for future poor maintainers.
You can only do the “what” with clearer code. The “why” needs some documentation. Even if it is obvious what the strange conditionals do, someone needs to have written down that this particular code is there because the special exemption from important tariffs of cigarettes due to the trade agreement between Serbia and Tunis that was valid between the years years 1992 and 2007.
This is where a good comment really can help! And in these types of domains I would guess/hope that there exists some project master list to crossref that will send both developers and domain experts to the same source for "tariff-EU-92-0578" specifically the section 'exemptions'. So the comment is not not just a whole paragraph copied in between a couple of /*/
