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n的范围是小于101010^{10}1010 抛弃ees和洲阁筛，拥抱min_25 代码： #include<cstdio> #include<cstring> #include<iostream> #include<cmath> #include<vector> #include<algorithm> #define IN...

Problem Description One day, Touma Kazusa encountered a easy math problem. Given n and k, she need to calculate the following sum modulo 1e9+7. ∑i=1n∑j=1ngcd(i,j)klcm(i,j)[gcd(i,j)∈prime]%(1e9+7)∑_{i=...