#include <fstream>

using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
unsigned long long sum;
int n,i,j;
int phi[1000005];
int main()
{
    f>>n;
    phi[1]=1;
    for (i=2;i<=n;i++)
    {
        phi[i]=i-1;
    }
    for (i=2;i<=n;i++)
    {
        for (j=2*i;j<=n;j+=i)
        {
            phi[j]-=phi[i];
        }
    }
    for (i=1;i<=n;i++)
    {
        sum+=phi[i];
    }
    g<<sum*2-1;
    return 0;
}