#include<fstream>
using namespace std;

int v[1000001];

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

    int i, j, n;
    long long nr = 0;

    f>>n;
    for (i = 1; i <= n; ++i)
        v[i] = i-1;
    for (i = 2; i <= n; ++i)
            {
                for (j = 2*i; j <= n; j += i)
                v[j] = v[j] - v[i];
                nr = v[i] + nr;
            }
    g<<1+2*nr;
}