#include <fstream.h>
long n,x=1,i;

void cit()
{ifstream f("fractii.in"); f>>n; f.close();}

void afis()
{ofstream g("fractii.out");
 g<<x<<'\n'; g.close();}

long f(long n)
{long d=2,p=1;
 while(n>1)
  {if(n%d==0)
    {n/=d; p*=(d-1);
     while(n%d==0) {p*=d; n/=d;}
    }
   d++;
  }
 return p;
}

int main()
{cit();
 for(i=2;i<=n;i++) x+=2*f(i);
 afis();
 return 0;
}