问题：
Amateur astronomers Tom and Bob try to find radio broadcasts of extraterrestrial civilizations in the air. Recently they received some strange signal and represented it as a word consisting of small letters of the English alphabet. Now they wish to decode the signal. But they do not know what to start with.
They think that the extraterrestrial message consists of words, but they cannot identify them. Tom and Bob call a subword of the message a potential word if it has at least two non-overlapping occurrences in the message.
For example, if the message is “abacabacaba”, “abac” is a potential word, but “acaba” is not because two of its occurrences overlap.
Given a message m help Tom and Bob to find the number of potential words in it.
Input
Output
Sample Input
abacabacaba
Sample Output
15
题意：
求字符串里最长的不相交重复字串的长度。
思路；
后缀自动机，记录每个状态的最先出现和最后一次出现的位置，就可以判断是否出现了多次，以及是否相交。