#include <ifstream>
using namespace std;
unsigned long long sol;
int n,i,v[1000001],j;
int main()
{
fin>>n;
for (i=1;i<=n;i++) v[i]=i-1;
for (i=2;i<=n;i++)
for (j=i+i;j<=n;j+=i)
v[j]-=v[i];
for (i=2;i<=n;i++) sol+=v[i];
sol*=2;sol++;
fout<<sol
}