#include <stdio.h>
#include <stdlib.h>

int main() {
	int *a, i, j, n;
	long long nr = 1;

	freopen("fractii.in", "r", stdin);
	freopen("fractii.out", "w", stdout);

	scanf("%i", &n);

	a = (int *)malloc((n + 1) * sizeof(int));
	for (i = 1; i <= n; ++i) {
		a[i] = i - 1;
	}

	for (i = 2; i <= n; ++i) {
		for (j = i + i; j <= n; j += i) {
			a[j] -= a[i];
		}
		nr += 2 * a[i];
	}

	printf("%lli", nr);

	return 0;

}