#include <iostream>
#include <fstream>
#define NUM 1000005
int phi[NUM];
int n;
long long sum;
using namespace std;
int main()
{
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    f >> n;

    for(int i = 1; i <= n; ++i)
        phi[i] = i;
    for(int i = 2; i <= n; ++i)
        if(phi[i] == i)
            for(int j = i; j <= n; j += i)
            {
                // phi[j] = phi[j] * (1 - 1 / i)
                phi[j] /= i;
                phi[j] *= (i - 1);
            }
    for(int i = 2; i <= n; ++i)
    {
        sum += phi[i];
    }
    g << 1 + 2 * sum;
    f.close();
    g.close();
}