#include<fstream>

using namespace std;
 
long phi[1000000];
long long s,n;
int i,j;

int main()
{  
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");  
   fin>>n;
 
   for(i=2;i<=n;i++)
       phi[i] = i-1;
     
    for(i=2;i<=n;i++)
      for(j=2*i;j<=n;j+=i)
           phi[j] = phi[j] - phi[i];
        
for(i=2;i<=n;i++)
   s+=phi[i];

  fout<<2*s+1<<"\n";
     system("pause");
return 0;
}