Andrey,
Ah, I see. Well, I guess I like both teaching and research. I don't have enough experience with either to do which I prefer more, or whether I would be happy doing just one of them for the rest of my life. But I would definitely be fascinated by the work on my PhD thesis. By the way, I did very well in national science fairs in high school (with a discrete mathematics topic). I mention this just to say that I love research and that I'm self-motivated to learn. It was poor health that derailed my plans earlier in life to get a PhD.
Regarding my love for teaching, I have tutored high school students in algebra and I'm currently tutoring a doctor in Python programming. I love this. So note--I don't need to be teaching an advanced topic to be happy. I'm fascinated by how to make a topic understandable, whether it would be teaching a graduate-level class, or figuring out how to help high school students who struggle with algebra.