—— 请按键盘 空白键 开始游戏 ——

The only way to learn mathematics is to do mathematics.
Sustainability is no longer an option; it's a responsibility we owe to future generations.
Rule of 7 in research. You can find out anything if you are willing to go seven levels. If the first source you ask doesn’t know, ask them who you should ask next, and so on down the line. If you are willing to go to the 7th source, you’ll almost always get your answer.