bzoj 2818 gcd 线性欧拉函数

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define mod 1000000009
#define inf 999999999
#define esp 0.00000000001
//#pragma comment(linker, "/STACK:102400000,102400000")
const int N=1e5,M=1e7+1000;
ll p[M],ji;
bool vis[M];
ll phi[M];
void get_eular(int n)
{
    ji = 0;
    memset(vis, true, sizeof(vis));
    for(int i = 2; i <= n; i++)
    {
        if(vis[i])
        {
            p[ji ++] = i;
            phi[i] = i - 1;
        }
        for(int j = 0; j < ji && i * p[j] <= n; j++)
        {
            vis[i * p[j]] = false;
            if(i % p[j] == 0)
            {
                phi[i * p[j]] = phi[i] * p[j];
                break;
            }
            else
            phi[i * p[j]] = phi[i] * phi[p[j]];
        }
    }
}
ll sumphi[M];
int main()
{
    ll x,y,z,i,t;
    get_eular(10000100);
    sumphi[0]=1;
    for(i=1;i<=10000000;i++)
    sumphi[i]=sumphi[i-1]+phi[i];
    while(~scanf("%lld",&x))
    {
        ll ans=0;
        for(i=0;p[i]<=x;i++)
        ans+=2*sumphi[x/p[i]]-1;
        printf("%lld\n",ans);
    }
    return 0;
}