4755. 快速荷叶叶变换

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <cmath>
 4 #define mo 1000000007
 5 #define LL long long
 6 using namespace std;
 7 LL n,m,ans1,ans2;
 8 
 9 LL Calc(LL n){
10     LL i=1,sum=0;
11     for(;i<=n;){
12         LL k=n/i,kk=n/k;
13         sum=(sum+k*(i+kk)*(kk-i+1)/2)%mo;
14         i=kk+1;
15     }
16     sum=((n*n%mo-sum)%mo+mo)%mo;
17     return sum;
18 }
19 
20 int main(){
21     scanf("%lld%lld",&n,&m);
22     ans1=Calc(n);
23     ans2=Calc(m);
24     cout<<(ans1*ans2)%mo;
25 }