#include <fstream>

using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
long long n,t=1;
int main()
{f>>n;
for(long long i=2;i<=n;i++)
{
    long long aux=i;
    long long p=i;
    if(aux%2==0){p=p/2;
               while(aux%2==0)aux=aux/2;}
     long long d=3;
     while(aux!=1)
       {
           if(aux%d==0){while(aux%d==0)aux=aux/d;
                        p=p*(d-1)/d;}
        d+=2;
       }
       t=t+2*p;
}

    g << t;
    return 0;
}