#include <fstream>

using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
const int VM=1000005;
int e[1000005];
int main()
{
    int n,i;
    in>>n;
    e[1]=1;
    for (int i = 2; i < VM; i++)
    {
        e[i] = i;
    }
    for (int i = 2; i < VM; i++)
    {
        if (e[i] == i)
        {
            for (int j = i; j < VM; j += i)
            {
                e[j] = e[j] / i * (i - 1);
            }
        }
    }
    long long s=0;
    for (int i=1;i<=n;i++)
    {
        s=s+e[i];
    }
    out<<2*s-1;
    return 0;
}