#include<fstream>
using namespace std;
int main()
{
    ifstream read("fractii.in");
    ofstream write("fractii.out");
    int N;
    read>>N;
    int Phi[N+1];
    long long int r(0);
    for (int i=0 ; i<=N ; ++i)
    {
        Phi[i]=i;
    }
    for( int p=2 ; p<=N ; ++p )
    {
        if(Phi[p]==p)
        {
            for(int i=p ; i<=N ; i=i+p)
            {
                Phi[i]=Phi[i] / p * (p-1);
            }
        }
    }
    for(int i=2 ; i<=N ; ++i)
    {
        r = r + Phi[i];
    }
    write << 2 * r + 1;
    return 0;
}