#include <fstream>

using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");

long long e [1000001];

int main()
{
    long long n, s = 0, i, j;
    in >> n;
    for (i = 2;i <= n; i++)
    {
        e[i] = i;
    }
    for (i = 2;i <= n; i++)
    {
        if(e[i] == i)
        {
            for(j = i;j <= n; j += i)
            {
                e[j]= e[j] / i * (i-1);
            }
        }
    }
    for(i = 1;i <= n;i++)
    {
        s=s+e[i];
    }
    out << s * 2 + 1;
    return 0;
}