#include <fstream>

using namespace std;

ifstream cin("fractii.in");
ofstream cout("fractii.out");

#define int long long
const int nMax=1e6;
int phi[nMax+5];

void make_phi(int n)
{
  for(int i=2;i<=n;i++)
    phi[i]=i;
  for(int i=2;i<=n;i++)
  {
      if(phi[i]==i)
      {
        for(int j=i;j<=n;j+=i)
          phi[j]=phi[j]/i *(i-1);
      }
  }
}

signed main()
{
    int n;
    cin>>n;
    make_phi(n);
    int ans=0;
    for(int i=2;i<=n;i++)
      ans+=2*phi[i];
    cout<<ans+1;
    return 0;
}