#include <fstream>

#define MAX 1000001
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");

int main(){
	long long answer=0,ciur[MAX],i,j,n;
	f >> n;

	for (i = 1; i <= n; i++)
		ciur[i] = i;

	for (i = 2; i <= n; i++){
		if (ciur[i] == i){
                for (j = i; j <= n; j += i){
				ciur[j] =(ciur[j] / i)*(i - 1);
			}
		}
	}
	for (i = 2; i <= n; i++){
		answer += ciur[i];

	}
	g << 2*answer+1;

	return 0;
}