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#include <bits/stdc++.h>
using namespace std;
vector<int> ph;
void fracti(int n)
{
for(int i=0; i<=n; i++)
ph[i]=i;
for(int i=2; i<=n; i++)
{
if(ph[i]==i)
{
for(int j=i; j<=n; j+=i)
ph[j]=ph[j]-ph[j]/i;
}
}
}
int main()
{
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int n;
fin>>n;
ph = vector<int>(n+1);
fracti(n);
long long count=1;
for(int i=2; i<=n; i++)
{
count=count+2*ph[i];
}
fout<< count;
}