#include<fstream>
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int N,phi[1000001],s;
int main(){ 	
   cin>>N;              
   //daca i e prim phi[i]=phi=i-1
   for (int i = 1; i <= N; ++i)
    phi[i] = i-1;
    for (int i = 2; i <= N; ++i)
    for (int j = 2*i; j <= N; j += i)
                      phi[j] -= phi[i];
		   for(int i=2;i<=N;i++)
		                 s+=phi[i];
		  s=s*2+1;     
		cout<<s;
	cin.close();
	cout.close();		      
   return 0;
}