摘要： \(\text{Solution}\) 容易发现答案为 \(\sum_{x = 1}^n\sum_{y = 1}^m[\gcd(x,y) = 1][\gcd(y,k) = 1]\) \(=\sum_{x = 1}^n\sum_{y = 1}^m\sum_{d|\gcd(x,y)}\mu(d)\sum 阅读全文

摘要： \(\text{Code}\) #include<cstdio> #include<tr1/unordered_map> #define LL long long using namespace std; const int M = 5e6; int vis[M + 5],p[M + 5],tot, 阅读全文