Educational Codeforces Round 36

#include<bits/stdc++.h>
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define pi acos(-1.0)
#define ll long long
#define mod 1000000007
#define C 0.5772156649
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1
#define pil pair<int,ll>
#define pii pair<int,int>
#define ull unsigned long long
#define base 1000000000000000000
#define fio ios::sync_with_stdio(false);cin.tie(0)

using namespace std;

const double g=10.0,eps=1e-12;
const int N=2000000+10,maxn=400000+10,inf=0x3f3f3f3f;

int mu
,prime
;
bool mark
;
void init()
{
mu[1]=1;
int cnt=0;
for(int i=2;i<N;i++)
{
if(!mark[i])prime[++cnt]=i,mu[i]=-1;
for(int j=1;j<=cnt;j++)
{
int t=i*prime[j];
if(t>N)break;
mark[t]=1;
if(i%prime[j]==0){mu[t]=0;break;}
else mu[t]=-mu[i];
}
}
}
ll quick(ll a,ll b)
{
ll ans=1;
while(b)
{
if(b&1)ans=ans*a%mod;
a=a*a%mod;
b>>=1;
}
return ans;
}
ll f
,ans
;
int main()
{
init();
ll n,k;
scanf("%lld%lld",&n,&k);
for(int i=0;i<=k;i++)f[i]=quick(i,n);
for(int i=1;i<=k;i++)
{
for(int j=1;j<=k;j++)
{
if(i*j>k)break;
ans[i*j]+=mu[j]*(f[i]-f[i-1]);
ans[i*j]%=mod;
}
}
//    for(int i=1;i<=k;i++)printf("%d\n",ans[i]);
for(int i=1;i<=k;i++)ans[i]=(ans[i-1]+ans[i])%mod;
ll res=0;
for(int i=1;i<=k;i++)
{
ans[i]=(ans[i]+mod)%mod;
res=(res+(ans[i]^i))%mod;
}
printf("%lld\n",res);
return 0;
}
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