#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
long long j,i,n, v[1000001],s;
int main()
{f>>n;
for(i=2;i<=n;i++)
v[i]=i-1;
for(i=2;i<=n;i++)
{s=s+v[i];
for(j=2*i;j<=n;j=j+i)
v[j]=v[j]-v[i];
}
g<<s*2+1;
return 0;

}