#include <fstream>
#define NM 1000002

using namespace std;

int phi[NM];

int main()
{
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
    long long rez = 1;
    int n;
    fin >> n;
    phi[1] = 1;
    for (int i = 2; i <= n; i++)
    {
        int k = 1;
        phi[i] += i - 1;
        rez += phi[i];
        for (int j = 2; i * j <= n; j++)
        {
            phi[i * j] -= phi[i];
        }
    }
    fout << rez * 2 - 1;

    return 0;
}