#include <fstream>

using namespace std;

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

    int n;
    f >> n;

    int e[1000001];
    for(int i = 2; i <= n; i++)
        e[i] = i;

    for(int i = 2; i <= n; i++)
        if(e[i] == i)
            for(int j = i; j <= n; j += i)
                e[j] = e[j] / i * (i - 1);
 
    unsigned long nr = 0;
    for(int i = 2; i <= n; i++)
        nr += e[i] - 1;

    unsigned long fr = nr * 2 + n * 2 - 1;
    g << fr;
    f.close();
    g.close();
    return 0;
}