#include<fstream>
using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

int main()
{

    int n;
    fin >> n;


    int phi[n+3];
    for (int i = 1; i <= n; i++)
    {
        phi[i] = i - 1;
    }

    phi[1] = 1;

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

    long long ans = 0;
    for (int i = 2; i <= n; i++)
    {
        ans += 2 * phi[i];
    }
    ans += phi[1];

    fout << ans;

    fin.close();
    fout.close();
    return 0;
}