摘要：http://codeforces.com/contest/235/problem/E远距离orz......rng_58证明可以见这里（可能要FQ才能看到）还是copy一下证明吧：记$$f(a,b,c)=\sum\limits_{i=1}^{a}\sum\limits_{j=1}^{b}\sum\... 阅读全文

摘要：http://www.lydsy.com/JudgeOnline/problem.php?id=2005莫比乌斯函数。不妨设N>=M。我们发现，坐标(x,y)到(0,0)的连线上有gcd(x,y)个点（包含自己）。所以答案就是：$$\sum_{1\leq x\leq N,1\leq y\leq M}... 阅读全文

摘要：#include#include#include#include#include#include#include#include#include#include#include#include#include#include#include#include#include#include#inclu... 阅读全文