#include <vector>
#include <fstream>
#include <numeric>
using namespace std;

int main(){
	ifstream f("fractii.in");
	int n = 0;
	f >> n;
	vector<int> phi(n+1, 0);
	iota(begin(phi), end(phi), 0);
	for(int i = 1; i <= n/2; ++i){
		for(int j = 2*i; j <= n; j+=i){
			phi[j] -= phi[i]; } }
	ofstream g("fractii.out");
	g << (2*accumulate(begin(phi), end(phi), 0ull)-1);
	return 0; }