#include<fstream.h>

int fi(long n)
 { long d=2;
   long P=n;
     while(n>1) { if(n%d==0) { P=P*(d-1)/d;
                               while(n%d==0)n/=d;
                             } 
                  else d++;
                } 
   return P;
 }                       

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

int main()

{  long i,a,n;
   f>>n;
   a=1;
   for(i=1;i<n;i++) a+=2*fi(i+1);
   g<<a;                   
   f.close();
   g.close();
   return 0;
}