#include <fstream>
using namespace std;
  
ifstream f("fractii.in");
ofstream g("fractii.out");
  
int n, v[1000002];
unsigned long long rez;
  
int main()
{
    f>>n;
    for (int i=2; i<=n; i++) v[i]=i-1;
    for (int i=2; i<=n; i++)
    {
        rez+=v[i];
        for (int j=i+i; j<=n; j+=i) v[j]-=v[i];
    }
    g<<rez*2+1;
    return 0;
  
}