#include<iostream>
#include<fstream>
#define NN 1000001


using namespace std;
ofstream out("fractii.out");

int prim[NN],function[NN],n,ans;

void read();
void solve();

int main()
{
	read();
	solve();
	out<< 1+ ( ans << 1 ) <<'\n';
	
	
	return 0;
}


void read()
{
	ifstream in("fractii.in");
	in>>n;
	for(int i=2;i<=n;i++)
		function[i]=i;
}


void solve()
{
	for(int i=2; i<=n ;++i)
	{
		if( !prim[i] )
		{
			
			for(int j=i; j<=n ;j+=i)
			{
				prim[j]=1;
				function[j] /=i;
				function[j] *= (i-1 );
			}
		}
		ans+=function[i];
	}
}