#include <fstream>
using namespace std;
long long c1[1000005];
bool c2[1000005];
int main()
{
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    long long i,n,j,p,nrf;
    f>>n;nrf=1+(2*(n-1));
    for (i=2;i<=n;i++) c1[i]=n-2;
    for (i=2;i<=n/2+(n%2);i++)
    {
        if (!c2[i])
        {
            p=n/i-1;c1[i]-=p;
            for (j=2*i;j<=n;j+=i)
            {
                c2[j]=1;
                c1[j]-=p;
            }
        }
    }
    for (i=2;i<=n;i++)
        nrf+=c1[i];
    g<<nrf<<'\n';
    f.close();
    g.close();
    return 0;
}