要写一封好的情书，你应该在不知道要说什么的情况下开始写，然后在不知道自己写了什么的情况下结束。
To write a good love letter， you ought to begin without knowing what you mean to say， and to finish without knowing what you have written.
In the realm of computational complexity, every problem is a universe waiting to be explored.
符号是思维的媒介。