#include <fstream>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

int main()
{
    int n,i,j;
    fin>>n;
    long long int ct=0;
    int phi[n+1];
    for (i=1; i<=n; i++)
    {
        phi[i]=i;
    }
    for (i=2; i<=n; i++)
    {
        if (phi[i]==i)
        {
            for (j=i; j<=n; j+=i)
            {
                phi[j]/=i;
                phi[j]*=(i-1);
            }
        }
    }
    for (i=1; i<=n; i++)
    {
        ct+=phi[i];
    }
    fout<<2*ct-1;
}