#include <iostream>
#include <fstream>
int phi[1000010] = {};

int main()
{
	std::ifstream fisier_in("fractii.in");
    std::ofstream fisier_out("fractii.out");
    long long int sol = 0;
    int n;
    fisier_in>>n;
    for(int i =2; i<=n;i++){
        phi[i]=i-1;
    }
    for(int i = 2; i<=n;i++)
    {
        sol = sol + phi[i];
        for(int j=2*i;j<=n;j=j+i)
        {
        	phi[j]=phi[j]-phi[i];
		}
    }
    sol = 2 * sol + 1;
    //std::cout<<sol;
    fisier_out<<sol;
	return 0;	
}