#include <fstream>
#define LL long long
#define MAX 1000000
using namespace std;
ifstream fi("fractii.in");
ofstream fo("fractii.out");

LL phi[MAX+5];
int n;

void getPhi()
{
    for (int i=0; i<=n; i++)
        phi[i]=i;
    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);
}

int main()
{
    fi.sync_with_stdio(false);
    fo.sync_with_stdio(false);
    fi>>n;
    getPhi();
    LL rez=0;

    for (int numarator=2; numarator<=n; numarator++)
        rez+=phi[numarator];
    rez=rez*2+1;
    fo<<rez;
    fi.close();
    fo.close();
    return 0;
}