#include <fstream>

using namespace std;

int main(){

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

	int n;
	fin >> n;
	fin.close();

	int* phi = new int[n+1];
	for (int i=1; i<=n; i++) phi[i] = i;

	long long result = 0;
	for (int i=2; i<=n; i++){
		if (phi[i] == i)
			for (int j=i; j<=n; j+=i)
				phi[j] = phi[j] / i * (i-1);
		
		result += phi[i];	
	}

	fout << result * 2 + 1;
	fout.close();

	return 0;
}