#include <stdio.h>
#include <stdlib.h>
#define LEN 1000001

int n, count;
char* phi = (char *)calloc(LEN, sizeof(char));

int
main(void)
{
	int i, j;
	freopen("fractii.in", "r", stdin);
	freopen("fractii.out", "w", stdout);
	
	scanf("%d", &n);

	for (i = 1; i <= n; i++) 
		phi[i] = i;

	for (i = 2; i <= n; i++)
		if (phi[i] == i)
			for (j = i; j <= n; j += i) 
				phi[j] /= i, phi[j] *= (i - 1);

	for(i = 2; i <= n; i++)
		count += 2 * phi[i];
	
	printf("%d ", count + 1);

	return 0;
}