/********************
    Created by Sburly
********************/
#include <fstream>

using namespace std;

int main()
{
    ifstream f("fractii.in");
    ofstream g("fractii.out");

    long long int n;
    f >> n;
    long long int totient[n+1];
    long long int sol = 0;


    for (long int i = 1; i <= n; ++i)
        totient[i] = i-1;
    for (long int i = 2; i <= n; ++i)
    {
        sol+=totient[i];
        for (long int j = 2*i; j <= n; j += i)
            totient[j] -= totient[i];
    }
    g << sol*2+1;

    return 0;
}