#include <bits/stdc++.h>

using namespace std;

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

#define int long long

int NMAX = 1e6;

int phi[1000005];

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

signed main()
{
    prec_phi();
    int n;
    in >> n;
    int sumphi = 0;
    for (int i = 1; i <= n; i++)
        sumphi += phi[i];
    out << 2 * sumphi - 1;
    return 0;
}