#include <stdio.h>
#include <math.h>

#define N 1000000

int main(void)
{
	int i, j, n, rt;
	int v[10000001];
	long long s = 0;


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

	scanf("%d", &n);

	rt = sqrt(n);

	v[1] = 1;

	for(i = 2; i <= n; i++)
	{
		if(v[i] == 0)
		{
			v[i] = i - 1;
			for(j = i + i; j <= n; j+=i)
				if(v[j] == 0)
					v[j] = j - j/i;
				else
					v[j] = v[j] - v[j]/i;
		}
	}
	for(i = 2; i <= n; i++)
		s += v[i];

	printf("%lld", 2*s + 1);
}