#include <fstream>
using namespace std;

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

long long max1=0;
int v[1000001], n, i, j;

int main()
{
    f>>n;
    for (i=2; i<=n; i++)
        v[i] = i-1;
    for (i=1; i<=n; i++)
    {
        max1 += v[i];
        for (j = i+i; j<=n; j += i)
            v[j] -= v[i];
    }
    max1 = max1 * 2 + 1;
    g<<max1;
    return 0;
}