#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int phi[1000001];
int main()
{
    int N,k=-1,j;
    f >> N;
    for (int i=1; i<=N; i++) phi[i]=i;
    for (int i=2; i<=N; i++)
        if (phi[i]==i)
            for (j=i; j<=N; j+=i) phi[j] /=i, phi[j] *= (i-1);

    for(int i=1; i<=N; i++)
        k+=phi[i]*2;
    g << k;
    return 0;
}