Find the communication formula: the lowest price between the previous A day and the previous (A+4) day.

Learning these things will waste you a lot of time because you are going in the wrong direction. Those things were made by fortune tellers to deceive the blind. These people are needed in this market, so those smart people can buy cheaper stocks of excellent companies. If I were you, I would also try to fool other participants in this market with a few technical indicators and let them go astray. Only in this way can the market have high returns. If they spend all their time on basic research, the market will become more efficient. An effective market is not a good thing for smart people, because the price fluctuation is smaller and more reasonable, there are fewer stocks of cheap excellent companies, and our return on investment will be less. If they don't spend their time in the wrong direction, but study the fundamentals, then they can do well. Unfortunately, their efforts were in vain, far from success. As long as you study in the right direction, you will make progress and be close to success, but if you study in the wrong direction, you will make progress, but this progress is far from success.