BZOJ2226: [Spoj 5971] LCMSum

#include<cstdio>
#include<iostream>
#include<cmath>
#include<cstring>
using namespace std;
#define ll long long
char c;
inline void read(ll &a)
{a=0;do c=getchar();while(c<'0'||c>'9');
while(c<='9'&&c>='0')a=(a<<3)+(a<<1)+c-'0',c=getchar();}
inline void read(int &a)
{a=0;do c=getchar();while(c<'0'||c>'9');
while(c<='9'&&c>='0')a=(a<<3)+(a<<1)+c-'0',c=getchar();}
const
ll Maxn=1000001;
int Prime[Maxn];
ll Fai[Maxn];
bool Check[Maxn];
int tot;

int main()
{
int T;
int i,j,l;
ll k;
for(i=2;i<Maxn;i++)
{
if(!Check[i])Fai[i]=i-1,Prime[++tot]=i;
for(j=1;j<=tot&&(k=Prime[j]*1ll*i)<Maxn;j++)
{
Check[k]=true;
if(i%Prime[j]==0)
{
Fai[k]=Prime[j]*Fai[i];
break;
}
Fai[k]=(Prime[j]-1)*Fai[i];
}
}
Fai[1]=1;
for(i=Maxn-1;i!=1;i--)
Fai[i]*=i,Fai[i]>>=1;
Fai[3]=3;
Fai[2]=1;
read(T);
while(T--)
{
int n;
read(n);
ll ans=0;
int t=sqrt(n);
for(int i=1;i<t;i++)
if(n%i==0)
{
ans+=Fai[n/i];
ans+=Fai[i];
}
if(t*t==n)ans+=Fai[t];
else if(n%t==0)ans+=Fai[t],ans+=Fai[n/t];
ans*=n;
printf("%lld\n",ans);
}
return 0;
}