#include <fstream>
using namespace std;
int main()
{
    long long maxi=0;
    int n,a[1000001],i,j;
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    f>>n;
    for(i=2;i<=n;i++)
        a[i]=i-1;
    for(i=2;i<=n;i++)
    {
        maxi+=a[i];
        for(j=2*i;j<=n;j=j+i)
            a[j]=a[j]-a[i];
    }
    g<<(maxi*2+1);
    return 0;
}