#include <stdio.h>

#define MAXN (1 << 20)

int N;
long long rez;

int cnt[MAXN];

int main(void)
{
	freopen("fractii.in", "rt", stdin);
	freopen("fractii.out", "wt", stdout);

	int i, j;

	scanf("%d\n", &N);

	for(i = 2; i <= N; i++)
	{
		cnt[i] = i-1-cnt[i];
		for(j = 2; j*i <= N; j++)
			cnt[i*j] += cnt[i];
	}

	for(i = 2; i <= N; i++)
		rez += (long long)cnt[i]*2;
	rez++;

	printf("%lld\n", rez);

	return 0;
}