#include <fstream>
using namespace std;
int n,i,j,a[1000001];
long long s;

int main()
{
     ifstream f("fractii.in");
     ofstream g("fractii.out");
     f>>n;
     s=1;
     for(i=1;i<=n;i++)
                      a[i]=i-1;
     for(i=1;i<=n;i++)
                     { for(j=2*i;j<=n;j+=i)
                          a[j]=a[j]-a[i];          
                          s=s+2*a[i];
                     }                                       
     g<<s;
     return 0;
     
}