#include <fstream>

using namespace std;

ifstream cin ("fractii.in");
ofstream cout ("fractii.out");
const int NMAX = 1000005;

int e[NMAX];

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

int main()
{
    long long n, s = 0;
    cin >> n;
    int i;
    ciur();
     for (i = 1; i <= n; i++)
    {
        s += e[i];
    }
    cout << s * 2 + 1;
    return 0;
}