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#include <bits/stdc++.h>
using namespace std;
ifstream fin ("fractii.in");
ofstream fout ("fractii.out");
int phi[1000005],i,j,n,cnt;
int main()
{
fin>>n;
for (i=1;i<=n;i++) phi[i]=i;
for (i=2;i<=n;i++)
if (phi[i]==i)
{
for (j=i+i;j<=n;j+=i)
phi[j]-=(phi[j]/i);
phi[i]--;
}
cnt=1;
for (i=2;i<=n;i++) cnt+=phi[i]*2;
fout<<cnt;
return 0;
}