早知如此绊人心，何如当初莫相识。

摘要： 题意：输入a,b,l,r。机器先输入a个字符串，必须是字典序从低到高的，人再输入b个任意字符串，然后机器再输入a个，再人，但是机器输入的还有一个规则，就是从当前的字符串后a个，机器这次不能再输入 思路：机器输入的是固定的吧，所以重要是人的，我们输入的如果全是当前字符串的最后一个，那么肯定是最优的，而 阅读全文

摘要： On one quiet day all of sudden Mister B decided to draw angle a on his field. Aliens have already visited his field and left many different geometric 阅读全文

摘要： A. Mister B and Book Reading Mister B once received a gift: it was a book about aliens, which he started read immediately. This book had c pages. At f 阅读全文