#include <iostream>
#include <fstream>

using namespace std;

fstream f("fractii.in", ios::in), g("fractii.out", ios::out);

int i, j, v[1000001], n;

long long p = 1;

int main()
{
    f >> n;

    for (int i = 2; i <= n; i++)
        v[i] = i - 1;


    for (int i = 2; i <= n; i++)
    {
        p += v[i] * 2;
        for (int j = i * 2; j <= n; j += i)
        {
            v[j] -= v[i];
        }
    }
    g << p;
    return 0;
}