#include<fstream.h>
ifstream fin("fractii.in");
ofstream fout("fractii.out");
long n,i,s=1,j,p,d,putere,putere2;
int main()
{fin>>n;
 for(i=2;i<=n;i++)
  { j=i;p=1;d=2;
    while(j!=1)
    { putere=0;
      putere2=1;
      while(j%d==0)
      { putere++;
	putere2*=d;
	j=j/d;
      }
      if(putere!=0)p=p*(d-1)*(putere2/d);
      if(d==2)d++;else d+=2;
    }
    s+=p*2;
  }
fout<<s;
fin.close();
fout.close(); 
return 0;
}