Thanks to the introduction and basics, I was able to listen well! The polymorphism part was difficult, but I understood it well because the memory structure was explained well with pictures. I thought I understood it well, but it was difficult when I actually solved the problem.. I reviewed the last polymorphism example three times haha,, Actually, understanding it in your head and using it on a blank sheet of paper are different ㅜ ㅜ I will continue to follow the instructor's roadmap well! ! Thank you (I am also using the shortcut keys you taught me well)