#include <iostream>
#include <fstream>
#define NM 1000002
using namespace std;

int n, phi[NM];
long long rez = 1;

int main()
{
    ifstream fin ("fractii.in");
    ofstream fout ("fractii.out");
    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;
}