#include <fstream>
#define MAXN 1000005
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int v[MAXN],n;
long long sol;
int main()
{int i,j;
   cin>>n;
   for (i=2;i<=n;i++) v[i]=i-1;
   for (i=2;2*i<=n;i++) for (j=2*i;j<=n;j+=i) v[j]-=v[i];
   for (i=2;i<=n;i++) sol+=1LL*v[i];
   cout<<sol*2+1<<"\n";
   cin.close();
   cout.close();
   return 0;
}