—— 请按键盘 空白键 开始游戏 ——

在数学中,就像在生活中一样,最优雅的解决方案往往来自于对问题的深刻理解。
With a library you are free, not confined by temporary political climates. It is the most democratic of institutions because no one - but no one at all - can tell you what to read and when and how.