摘要：
Teacher Mai has a kingdom with the infinite area. He has n students guarding the kingdom. The i th student stands at the position (x i,y i), and his w 阅读全文
摘要：
Long long ago, there is a famous farmer named John. He owns a big farm and many cows. There are two kinds of cows on his farm, one is Friesian, and an 阅读全文
摘要：
The most exciting space discovery occurred at the end of the 20th century. In 1999, scientists traced down an ant like creature in the planet Y1999 an 阅读全文
摘要：
Once upon a time there was a greedy King who ordered his chief Architect to build a wall around the King's castle. The King was so greedy, that he wou 阅读全文