#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
long N,v[10000000],i,j,sol;

int main()
{ f>>N;
  for (i=1;i<=N;i++) v[i]=i;
  for (i=2;i<=N;i++) {
    if (v[i]==i)
        for (j=i;j<=N;j+=i)
        v[j]=v[j]/i*(i-1);
  }
  for (i=2;i<=N;i++)
    sol+=v[i];

  sol=sol*2+1;
  g<<sol;
  f.close();
  g.close();

    return 0;
}