#include<fstream.h>
#include<math.h>
long a[1000001],n,i,y,j,x,p,m,ok;
long long nr,rad;
int main()
{
ofstream out("fractii.out");
ifstream in("fractii.in");
in>>n;
a[1]=1;
for(i=2;i<=n;i++)
	{x=i;p=2;
	rad=sqrt(x);
	while(p<=rad&& x%p)p++;
	if(p>rad) a[i]=i-1;
	else
	{y=1;
	while(x%p==0)
	{y=y*p;
	x=x/p;
	}
	y=y/p;
	a[i]=(p-1*y*a[x];
	}

	}
	nr=1;
	for(i=2;i<=n;i++)
nr=nr+2*a[i];
out<<nr;
out.close();
in.close();
return 0;
}




return 0;
}