#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
unsigned long N,i,j,nr,v[1000000],suma;
int main() {
	in>>N;
	nr=1;
	for (i=1;i<=N;i++) 
		v[i]=i;
	for (i=2;i<=N;i++)
		if (v[i]==i)
			for (j=i;j<=N;j+=i) v[j]/=i, v[j]*=(i-1);

	suma=0;
	for(i = 1; i<=N; i++) 
		suma+=v[i];
	out<<suma*2-1;
	return 0;
}