#include <bits/stdc++.h>

using namespace std;

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

const int NMAX = 1000000;
int phi[NMAX + 5];

void fill_phi(int n)
{
    phi[1] = 1;
    phi[2] = 1;
    phi[3] = 2;
    int k;
    for(k = 4; k <= n; ++k)
    {
        ///calc phi[k] in baza val gasite anterior
        int d;
        bool ok = 1;
        for(d = 2; d*d <= k && ok; ++d)
        {
            if(k % d == 0)
            {
                ok = 0;
                int exponent = 1;
                int copie = k;
                while(copie % d == 0)
                {
                    exponent *= d;
                    copie /= d;
                }
                ///exponent = d^{v_d(k)}
                phi[k] = (d-1)*(exponent/d)*phi[k/exponent];
            }
        }
        if(ok == 1)
            phi[k] = k - 1;
    }
}

int main()
{
    int n, i;
    f >> n;
    fill_phi(n);
    long long suma = 0;
    for(i = 1; i <= n; ++i)
        suma += phi[i];
    g << 2*suma - 1;
    return 0;
}