#include <fstream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
long long n,i,j,phi[1000001],phif;
int main()
{
    fin>>n;
    phif=0;
    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=2;i<=n;i++)
        phif+=phi[i];
    fout<<2*phif+1;
    return 0;
}