I finished it in 2 days!! This time, I wanted to take the backend course, so I bought the course with the mindset of learning Java step by step, and I really understood it well and I feel like I have solidified my basics. It's a shame that the intermediate and advanced courses come out later, but I'm going to study the rest of the book and take the backend course. Thank you so much to instructor Kim Young-han, who always creates the best lectures!