bzoj3930

题解：

莫比乌斯函数

然而向我这种弱菜肯定选择暴力ｄｐ

代码：

#include<bits/stdc++.h>
const int N=,M=;
typedef long long ll;
using namespace std;
int n;
ll m,L,R,k,f[N];
ll power(ll x,int y)
{
    ll ans=;
    while (y)
     {
        if (y&)ans=ans*x%M;
        x=x*x%M;
        y>>=;
     }
    return ans;
}
int main()
{
    scanf("%d%lld%lld%lld",&n,&k,&L,&R);
    for (ll i=R-L;i>=;i--)
     {
        ll l=(L-)/(k*i),r=R/(k*i);
        f[i]=(power(r-l,n)-(r-l)+M)%M;
        for (int j=;i*j<=R-L;j++)f[i]=(f[i]-f[i*j]+M)%M;
     }
    if (L<=k&&k<=R)f[]++;
    printf("%d\n",f[]);
    return ;
}