#include <fstream>

using namespace std;

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

int a[1000001];

int main()
{
    long long n, s = 0;
    f >> n;
    for (int i = 2; i <= n; i++)
    {
        s += (a[i] += i - 1);
        for (int j = 2 * i; j <= n; j += i)
            a[j] -= a[i];
    }
    g << 1 + 2 * s;
    return 0;
}
// R(n) = 1 + 2 * sum(i = 1 : n, tot(i))
//tot(n) = n - sum(i = divizorii lui n : n, i)