#include <iostream>
#include <fstream>
using namespace std;

int phi(int n) {
	int result = n;
	for (int i=2; i*i<=n; ++i)
		if (n % i == 0) {
			while (n % i == 0)
				n /= i;
			result -= result / i;
		}
	if (n > 1)
		result -= result / n;
	return result;
}
int n,answer;
int main()
{
    ifstream fin("fractii.in");
    fin>>n;
    answer=3;
    for(int i=3;i<=n;i++){
        answer+=2*phi(i);
    }
    ofstream fout("fractii.out");
    fout << answer  << endl;
    return 0;
}