// Fractii.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include<iostream>
#include<conio.h>
using namespace std;

long n, i, j, phi[1000000], rez=0;

int _tmain(int argc, _TCHAR* argv[])
{cin>>n;
for(i=1;i<=n;i++)
	phi[i]=i;
for(i=2;i<=n;i++)
	if(phi[i]==i)
		for(j=i;j<=n;j+=i)
			phi[j]/=i, phi[j]*=(i-1);
for(i=2;i<=n;i++)
	rez+=phi[i];
cout<<rez*2+1;
getch();
return 0;
}