#include <cstdio>

int main() {
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	long long sum = 0;
	long n;
	int i,j;
	scanf("%ld", &n);
	long euler[1000001];
	for (i = 1; i <= n; i++)
		euler[i] = i;
	for (i = 2; i <= n ; i++) {
		if (euler[i] == i) {
			for (j = i; j <= n ; j += i) {
				euler[j] = euler[j] / i * (i-1);
			}
		}
		sum += euler[i];
	}
	printf("%lld\n", 2 * sum + 1);
	fcloseall();
	return 0;
}