#include <stdio.h>
#define NMAX 1000010

int main()
{
	freopen("fractii.in", "r", stdin);
	freopen("fractii.out", "w", stdout);
	int phi[NMAX];
	int n, i, j;
	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] = phi[j]/i*(i-1);

	long sum = 0;
	for (i=2; i<=n; ++i)
		sum += phi[i];
	sum *= 2;
	++sum;
	printf("%lld\n", sum);
	return 0;
}