#include<fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
bool t[100];
long long nr;
int N, phi[1000001];
int main ()
{
    f>>N;
    for (int i = 1; i <= N; ++i)
        phi[i] = i-1;
    for (int i = 2; i <= N; ++i)
        {for (int j = 2*i; j <= N; j += i)
            phi[j] -= phi[i];
            nr+=phi[i];}
    g<<1+2*nr;
}