A few days ago, the blog about the book "Looking for a challenge 2" was posted on Codeforces, I read a quarter of the book and found that the quality was really good. I talked with a few friends about the book and we decided to buy a "Looking for a challenge 1". At first we considered buying a paperback version, but it was quite expensive and I'm afraid that some problems may occur during the shipment from Poland to China.

After a few days I found the book "Looking for a challenge" was available on the website "http://ibuk.pl" for 66,50 zł, the cheapest I can find on the internet. So I purchased the book with a master card, and I was able to download the pdf version of the book. With the excitement,