#include<fstream>

using namespace std;
 
long fi[1000000];
long long s,x;
int i,j;

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

  fout<<2*s+1<<"\n";

return 0;
}