摘要：
There arenpeople andmpairs of friends. For every pair of friends, they can choose to become online friends (communicating using online applications) o... 阅读全文
摘要：
Gerald got a very curious hexagon for his birthday. The boy found out that all the angles of the hexagon are equal to. Then he measured the length of ... 阅读全文
摘要：
Today on a lecture about strings Gerald learned a new definition of string equivalency. Two stringsaandbof equal length are calledequivalentin one of ... 阅读全文