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