#include<fstream>
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
long long n,rez;
int a[1000500];
int main(){
	cin >>n;
	for (int  i = 2; i <= n; i++){
		a[i] = i;
		
	}
	for (int i = 2; i <= n; i++){
		if (a[i] == i)
		{
			for(int j = i; j <= n; j+=i){
				a[j]/=i;
				a[j]*=(i-1);
			}
		}
	}
	for(int i = 2; i <= n; i++){
		rez+=a[i];
	}
	cout << 2*rez + 1;
}