#include <iostream>
#include <fstream>
#define DN 1000005
using namespace std;

long long n,s[DN];

int main()
{
	ifstream f("fractii.in");
	ofstream g("fractii.out");
	f>>n;
	//cin>>n;
	int rez=0;
	for(int i=2; i<=n; ++i) s[i]=i-1;
	for (int i=2; i<=n; ++i) {
		rez+=s[i];
		for(int j=i+i; j<=n ; j+=i) s[j]-=s[i];
	}
	rez=(rez*2)+1;
	//cout<<rez;	
	g<<rez;
	return 0;
}