#include <fstream>
#define NM 1000005

using namespace std;

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

int n,i,v[NM],s,j;

int main()
{
    fin >> 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++)
      s+=v[i];
    s*=2;
    s++;
    fout << s << '\n';
    fin.close();
    fout.close();
    return 0;
}