#include <fstream>

using namespace std;

int a[1000005];

void Ciur()
{
    int i, j;
    for(i = 2; i <= 1000005; i++)
        a[i] = i - 1;
    for(i = 2; i <= 1000005; i++)
        for(j = i + i; j <= 1000005; j += i)
            a[j] -= a[i];
}

int main()
{
    int i, n;
    long long s = 1;
    ifstream fin("fractii.in");
    fin >> n;
    fin.close();
    Ciur();
    for(i = 2; i <= n; i++)
        s += 2 * a[i];
    ofstream fout("fractii.out");
    fout << s << "\n";
    fout.close();
    return 0;
}