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

#define NMAX 1000
int  p[]={2, 3 ,5 ,7 ,11 ,13 ,17 ,19 ,23 ,29 ,31 ,37 ,41 ,43 ,47 ,53 ,59 ,61 ,67 ,71 ,73 ,79 ,83 ,89 ,97 ,101 ,103 ,107 ,109 ,113 ,127 ,131 ,137 ,139 ,149 ,151 ,157 ,163 ,167 ,173 ,179 ,181 ,191 ,193 ,197 ,199 ,211 ,223 ,227 ,229 ,233 ,239 ,241 ,251 ,257 ,263 ,269 ,271 ,277 ,281 ,283 ,293 ,307 ,311 ,313 ,317 ,331 ,337 ,347 ,349 ,353 ,359 ,367 ,373 ,379 ,383 ,389 ,397 ,401 ,409 ,419 ,421 ,431 ,433 ,439 ,443 ,449 ,457 ,461 ,463 ,467 ,479 ,487 ,491 ,499 ,503 ,509 ,521 ,523 ,541 ,547 ,557 ,563 ,569 ,571 ,577 ,587 ,593 ,599 ,601 ,607 ,613 ,617 ,619 ,631 ,641 ,643 ,647 ,653 ,659 ,661 ,673 ,677 ,683 ,691 ,701 ,709 ,719 ,727 ,733 ,739 ,743 ,751 ,757 ,761 ,769 ,773 ,787 ,797 ,809 ,811 ,821 ,823 ,827 ,829 ,839 ,853 ,857 ,859 ,863 ,877 ,881 ,883 ,887 ,907 ,911 ,919 ,929 ,937 ,941 ,947 ,953 ,967 ,971 ,977 ,983 ,991 ,997 };
int num = 1;
long n, nr;
long long fr = 1;


int main()
{
	long i, ci, j, lim;
	long phi;
	freopen("fractii.in", "r", stdin);
	freopen("fractii.out", "w", stdout);
	scanf("%ld", &n);
	for ( i = 2; i <= n; i++)
	{
		ci = i;
		phi = i;
		lim = sqrt(ci);
		for ( j = 0; p[j] <= lim && ci > 1; j++)
		{
			if ( ci % p[j] ==0)
			{
				phi = phi / p[j] * ( p[j] - 1);
				while ( ci >1 && ci % p[j] == 0)
					ci /= p[j];
			}
		}
		if ( ci >1)
			phi = phi / ci * (ci - 1);

		fr += 2 * phi;
	}
	printf("%lld", fr);
	return 0;
}