#include<stdio.h>
#define Nmax 1000002
using namespace std;
int n;
long long p[Nmax];

int main()
{
	int i,j;
	long long s;
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d",&n);
	for(i=1;i<=n;++i)
		p[i]=i-1;
	s=0;
	for(i=2;i<=n;++i)
	{
		s+=p[i];
		for(j=i+i;j<=n;j+=i)
			p[j]-=p[i];
	}
	s=s*2+1;
	printf("%lld",s);
	fclose(stdin);
	fclose(stdout);
	return 0;
}