#include <iostream>
#include <fstream>

using namespace std;

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

const int NMAX = 1000000;
int v[NMAX + 1];

int N;

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

int main()
{
    int n;
    Euler(NMAX);
    f >> n;
    long long S = 1;
    for(int i = 2; i <= n; i++)
        S += 2 * v[i];
    g<<S;
    return 0;
}