理论计算机科学中的挑战不仅仅是解决问题，而是理解为什么它们难以解决。

In the part of this universe that we know there is great injustice， and often the good suffer， and often the wicked prosper， and one hardly knows which of those is the more annoying.

The past is a shadow that follows us, but it is up to us to decide whether it will darken our future.