#include<iostream>
#include<fstream>
using namespace std;
int v[1000004];
int main() {
	ifstream fi("fractii.in");
	ofstream fo("fractii.out");
	int n;
	int i, j;
	fi >> n;
	for (i = 2; i <= n; i++) {
		v[i] = i;
	}
	i = 2;
	while (i <= n) {
		for (j = i; j <= n; j+=i) {
			v[j] /= i;
			v[j] *= (i - 1);
		}
		while (v[i] != i && i <= n)
			i++;
	}
	long long sum = 0;
	for (i = 1; i <= n; i++) {
		sum += (long long) v[i];
	}
	fo << (long long) 2 * sum + 1;
	fi.close();
	fo.close(); 
	return 0;
}