#define NMAX 1024000

#include <fstream>

using namespace std;

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

int a[NMAX], n;

long long int sol;

int main()
{
	fin >> n;
	
	sol = 0;
	  
	for (int i = 1; i <= n ; ++i) a[i] = i;  
 
	for (int i = 2; i <= n; ++i)  
  		if (a[i] == i)  
    		for (int j = i; j <= n; j += i) a[j] = a[j] /i * (i - 1);  
 	for (int i = 1; i<= n; ++i) sol += a[i];
 	
 	sol = 2 * sol -1;
  
  	fout << sol;  
	
	fin.close();
	fout.close();
	
	return 0;
}