poj 2478(欧拉函数)

poj 2478
筛选法求欧拉函数

每个询问答案是$$\sum_{i=1}^n\varphi(i)$$

#include<cstdio>  
#include<algorithm>  
#include<cstring>  
#include<cmath>
#define ms(i,j) memset(i,j, sizeof i);
using namespace std;
#define ll long long
ll phi[1000000+5];
void phitable(ll n)
{
    for (int i=2;i<=n;i++) phi[i] = 0;
    phi[1] = 1;
    for (int i=2;i<=n;i++) if (!phi[i])
    for (int j=i;j<=n;j+=i) 
    {
        if (!phi[j]) phi[j] = j;
        phi[j] = phi[j]/i*(i-1);
    }
}
int main()  
{  
    phitable(1000000);
    int n;
    while (scanf("%d", &n)==1 && n)
    {
        ll tot = 0;
        for (int i=2;i<=n;i++) tot += phi[i];
        printf("%lld\n", tot);
    }
    return 0;  
}