#include <cstdio>

#define file_in "fractii.in"
#define file_out "fractii.out"

int n,v[1010000];

void citire()
{
	freopen(file_in,"r",stdin);
	freopen(file_out,"w",stdout);
	
	scanf("%d", &n);
}

void solve()
{
	int i,j;
	long long sol=0;
	
	for (i=2;i<=n;++i)
		 v[i]=i-1;
	
	for (i=2;i<=n;++i)
	{
		sol+=v[i];
		for (j=i+i;j<=n;j+=i)
			 v[j]-=v[i];
	}
	
	printf("%lld", sol*2+1);	
	
}

int main()
{
	citire();
	solve();
	
	fclose(stdin);
	fclose(stdout);
	
	return 0;
	
}