#include <fstream>

using namespace std;
const int N=1000001;
long long e[N];
int main()
{
  long long n,j,s=0,i;
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    f>>n;
    for (i = 1;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=2;i<=n;i++)
        s=s+e[i];
    g<<2*s+1;
    return 0;
}