#include<fstream>
using namespace std;
int main(){
	ifstream in("fractii.in");
	ofstream out("fractii.out");
	long long n, i, j, s=0, phi[1000000];
	in>>n;
	for(i = 1; i <= n; i++){
		phi[i] = i;
	}
	for(i = 2; i <= n; i++){
		if(phi[i] == i){
			for(j = i; j <= n; j+=i){
				phi[j] = phi[j] * (i - 1) / i;
			}
		}
	}
	for(i = 2; i <= n; i++){
		s+=phi[i];
	}
	out<<(2 * s) + 1;

	in.close();
	out.close();
	return 0;
}