#include <cstdio>

using namespace std;

long long int phi[1000001];
long long int sol = 1;

void indicator(long long int n)
{
	for (int i = 1;i <= n;++i)
		phi[i] = i - 1;
	for (int i = 2;i <= n;++i)
	{
		for (int j = 2 * i;j <= n;j += i)
			phi[j] -= phi[i];
		sol += 2*phi[i];
	}
}

int main()
{
	int n;
	freopen("fractii.in", "r", stdin);
	freopen("fractii.out", "w", stdout);
	scanf("%lld", &n);
	indicator(n);
	printf("%lld", sol);
	return 0;
}