#include<fstream>
using namespace std;
int x[1000010],n,i,j;
long long s;
int main()
{
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    f>>n;
    for(i=2;i<=n;++i)
{
        if(x[i]==0)
        {
            s+=i-1;
 
            for(j=i+i; j<=n; j+=i)
            {
                if(x[j]==0)
                    x[j]=j-(j/i);
               else
                    x[j]=x[j]-x[j]/i;
            }
        }
        else
            s += x[i];
    }
  g<<(2*s+1);
    return 0;
}