#include <fstream>
#include <set>

using namespace std;

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

long long n, a[1000005], ans;

int main()
{
    f >> n;

    for (int i = 1; i <= n; ++i) {
        a[i] = i;
    }

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

    for (int i = 2; i <= n; ++i) {
        ans += a[i];
    }

    g << ans * 2 + 1;

    return 0;
}