#include<fstream>
#define nmax 1000005
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int n;
int prim[nmax];
long long s;
void solve()
{
	int i,j,c1,c2;
	s=n*n;
	for(i=2;i<=n;i++)
		if(!prim[i])
		{
			for(j=i,c1=0,c2=0;j<=n;j+=i)
			{
				if(!prim[j])
					prim[j]=1;
				else
					c2++;
				c1++;
			}
			s-=c1*c1;
			s+=c1;
		}
	g<<s-(n-1)<<'\n';
}
int main()
{
	f>>n;
	solve();
	f.close();
	g.close();
	return 0;
}