#include <fstream>
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int n;
int j;
int v[1000001];
long long s;
int main()
{
    cin >> n;
    int i;
    s = 1;
    for (i = 1; i <= n; i++)
        v[i] = i;
    for (i = 1; i <= n; i++)
        for (j = i * 2; j <= n; j = j + i)
            v[j] = v[j] - v[i];
    for (i = 2; i <= n; i++)
        s = s + 2 * v[i];
    cout << s;
}