F题明显爆int的，但是用long long就wa
强烈要求rejudge!

include<bits/stdc++.h>

using namespace std;
const int N = 500009;
int p[N] = {1, 1}, prime[N], pcnt, phi[N] = {0, 1}, n;
long long sum[N] = {0, 1};
int main()
{
for(int i = 2; i < N; i++)
{
if(!p[i])
{
phi[i] = i - 1;
prime[pcnt++] = i;
}
for(int j = 0; j < pcnt && iprime[j] < N; j++)
{
p[iprime[j]] = 1;
phi[iprime[j]] = phi[i] * (prime[j]-1);
if(i % prime[j] == 0)
{
phi[iprime[j]] = phi[i] * prime[j];
break;
}
}
sum[i] = sum[i-1] + phi[i];
}
while(cin >> n)
cout << 2 * sum[n] + 1 << endl;
}