#include <iostream>
#include <fstream>

using namespace std;

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

int tot[1000005], n;

int main()
{
    long long rez = 0;
    fin >> n;

    for(int i=2; i<=n; i++)
        tot[i] = i;

    for(int i=2; i<=n; i++){
        if(tot[i] == i)
            for(int j=i; j<=n; j += i)
                tot[j] = tot[j]/i*(i-1);
        rez += tot[i];
    }

    fout<<(rez*2)+1;
}