#include <fstream>

using namespace std;

int v[1000001];

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

int main()
{
    int n,i,j;
    long long s=0;
    in>>n;
    for (i=1;i<=n;i++)
        v[i]=i;
    for (i=2;i<=n;i++)
    {
      if (v[i]==i)
        v[i]=i-1;
      for (j=2*i;j<=n;j+=i)
        v[j]=(v[j]/i)*(i-1);
    }
    for (i=1;i<=n;i++)
        s+=v[i];
    out<<s*2+1;
    return 0;
}