#include <fstream>

using namespace std;

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

const int nmax= 1000000;
int phi[nmax+1];

int main()
{
    int n;
    fin>>n;

    for ( int i= 1; i<=n; ++i )
        phi[i]= i;
    
    int sol= 1;
    for ( int i= 2; i<=n; ++i )
    {
        if ( phi[i]==i )
            for ( int j= i; j<=n; j+= i )
                phi[j]= phi[j]/i*(i-1);
        sol+= 2*phi[i];
    }

    fout<<sol;
    
    return 0;
}