#include <fstream>
using namespace std;
unsigned long long sol;
int n,i,v[1000001],j;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
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;
}