#include <fstream>

using namespace std;

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

long long n, s=1, phi[1000001];

int main()
{
    f>>n;

    for (int i = 1; i <= n; i++)
        phi[i] = i-1;

    for (int i = 2; i <= n; i++)
        {
            s+=phi[i]*2;

            for (int j = 2*i; j <= n; j += i)
                phi[j] -= phi[i];
        }

    g<<s;

    return 0;
}