http://www.lydsy.com/JudgeOnline/problem.php?id=4407
题意:
给下N,M,K.求
思路:
来自:http://blog.csdn.net/ws_yzy/article/details/50670213
#include<cstdio>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<cstring>
#define ll long long
const ll Mod=;
ll f[],sum[],p[],s[];
bool mark[];
ll K,n,m;
ll read(){
ll t=,f=;char ch=getchar();
while (ch<''||''<ch){if (ch=='-') f=-;ch=getchar();}
while (''<=ch&&ch<=''){t=t*+ch-'';ch=getchar();}
return t*f;
}
ll Pow(ll x,ll y){
ll res=;
while (y){
if (y%) res=(res*x)%Mod;
y/=;
x=(x*x)%Mod;
}
return res;
}
void init(){
f[]=;
for (int i=;i<=;i++){
if (!mark[i]){
p[++p[]]=i;
s[p[]]=Pow(i,K);
f[i]=s[p[]]-;
}
for (int j=;j<=p[]&&p[j]*i<=;j++){
mark[p[j]*i]=;
if (i%p[j]==){
f[i*p[j]]=f[i]*s[j]%Mod;
break;
}
f[i*p[j]]=f[i]*f[p[j]]%Mod;
}
}
for (int i=;i<=;i++)
sum[i]=sum[i-]+f[i]%Mod;
}
int main(){
int T=read();K=read();
init();
while (T--){
n=read();m=read();
if (n>m) std::swap(n,m);
int j=;
ll ans=;
for (int i=;i<=n;i=j+){
j=std::min(n/(n/i),m/(m/i));
ans+=(((n/i)*(m/i)%Mod)*(sum[j]-sum[i-]))%Mod;
ans%=Mod;
}
printf("%lld\n",ans);
}
return ;
}