#include <iostream>
#include <fstream>
#include <cmath>

using namespace std;

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

int phi[1000005];

int main()
{
    long long s = 1;
    int n, i, j;
    in >> n;
    for (i = 1; i <= n; ++i)
        phi[i] = i - 1;
    for (i = 2; i <= n; ++i)
    {
        for (j = 2 * i; j <= n; j += i)
            phi[j] -= phi[i];
    }
    for (i = 1; i <= n; ++i)
        s += phi[i] * 2;
    out << s;
    return 0;
}