Uva 10820 Send a Table(欧拉函数)

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
#include<cmath>
#include<map>
#include<set>
#include<list>
#include<deque>
#include<vector>
#include<algorithm>
#include<stack>
#include<queue>
#include<cctype>
#include<sstream>
using namespace std;
#define pii pair<int,int>
#define LL long long int
const double eps=1e-10;
const int INF=1000000000;
const int maxn=50000+10;
int n,phi[maxn];
int main()
{
    //freopen("in2.txt","r",stdin);
    memset(phi,0,sizeof(phi));
    for(int i=2;i<maxn;i++)
    {
        if(phi[i]==0)
        {
            for(int j=i;j<maxn;j+=i)
            {
                if(phi[j]==0) phi[j]=j;
                phi[j]=phi[j]/i*(i-1);
            }
        }
    }
    while(scanf("%d",&n)==1&&n)
    {
        LL ans=1;
        for(int i=2;i<=n;i++)
        {
            //cout<<i<<‘-‘<<phi[i]<<endl;
            ans+=(LL)phi[i]*2;
        }
        cout<<ans<<endl;
    }
    return 0;
}