#include <fstream>
#define NM 1000010

using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");

int N, i, j;
long long ANS;
int Phi[NM];

int main ()
{
    f >> N;
    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]=Phi[j]/i*(i-1);

    for (i=2; i<=N; i++)
        ANS+=2LL*Phi[i];

    g << ANS+1 << '\n';

    f.close();
    g.close();

    return 0;
}