#include <fstream>

using namespace std;

ifstream cin("fractii.in");
ofstream cout("fractii.out");
int n;
int j;
int v[1000001];
int 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] --;
 for (i = 2; i <= n; i ++)
    s = s + 2 * v[i];
 cout << s;
}