#include <fstream>
using namespace std;

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

int n,i,phi[1000100],p,j;
long long s;

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