摘要：
Edward has a permutation {a1, a2, … an}. He finds that if he connects each pair (ai, aj) such that i < j and ai > aj, he will get a graph. For example 阅读全文
摘要：
有用的表格 详细 http://blog.miskcoo.com/2014/07/fft-prime-table 阅读全文