#include <stdio.h>
#include <stdlib.h>
#define LEN 10000001

int n;
unsigned long long count, i, j;

int
main(void)
{
	char* phi = (char *)malloc(LEN * sizeof(char));

	freopen("fractii.in", "r", stdin);
	
	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);
		count += (long long)2 * phi[i];
	}

	fprintf(freopen("fractii.out", "w", stdout), "%lld", count + 1);

	return 0;
}