#include<iostream>
#include<fstream>

using namespace std;

ifstream in("fractii.in");
ofstream out("fractii.out");

int i,j,n,cnt=0,v[1000000];

int main (void)
{
	in>>n;

	for(i=1;i<=n;i++)
		v[i]=i;
	for(i=2;i<=n;i++)
		if(v[i]==i)
			for(j=i;j<=n;j+=i)
				v[j]/=i, v[j]*=(i-1);
	for(i=2;i<=n;i++)
		cnt=cnt+v[i];
	out << (2*cnt)+1;

	in.close();
	out.close();

	return 0;
}