#include <fstream>
#include <vector>
#include <numeric>
#include <utility>
#include <iostream>

using std::cout;
using std::ifstream;
using std::ofstream;
using std::accumulate;
using std::vector;

int main(){
	ifstream f("fractii.in" );
	ofstream g("fractii.out");
	long long N = 0;
	f>>N;
	vector<long long> phi(N+1,0);
	for(long long i = 1;i<=N;i++){
		phi[i] = i;
	}
	long long counter = 0;
	for(long long i = 1;i<=N;i++){
		counter += phi[i];
		for(long long j = 2;i*j <= N;j++){
			phi[i*j] -= phi[i];
		}
	}
	g<<2*counter -1;
	return 0;
}