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#include<bits/stdc++.h>
#define maxN 1000005
using namespace std;
int Phi[maxN],sol,n;
int main()
{
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
scanf("%d",&n);
for(int i=1;i<=n;i++) Phi[i]=i;
for(int i=2;i<=n;i++)
{
if(Phi[i]==i)
{
for(int j=i;j<=n;j+=i)
{
Phi[j]=Phi[j]/i*(i-1);
}
}
}
for(int i=1;i<=n;i++)
{
sol=sol+Phi[i];
}
sol*=2;
sol--;
printf("%d\n",sol);
return 0;
}