#include<fstream>
using namespace std;
int v[1000];

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

int main()
{ 
  ifstream fin("fractii.in");
  ofstream g("fractii.out");
  int i;
  long long n, x=1;
  fin>>n;
  for(i=1;i<=n;i++) 
    x=x+2*fi(i+1);
  g<<x;
  fin.close();
  g.close();
  return 0;
}