#include<fstream>

using namespace std;

long long s,n;

long fi(long x)
{
	long nr=x,i=2;
	if(x%2==0)
	{
		nr/=2;
		while(x%2==0)x/=2;
	}
	i=3;
	while(i*i<=x)
	{
		 if(x%i==0)
		 {
			 nr/=i;
			 nr*=i-1;
			 while(x%i==0)x/=i;
		 }
		 i+=2;
	}
	if(x>1)
	{
		nr/=x;
		nr*=x-1;
	}
	return nr;
}


int main()
{
	long i;
	ifstream f("fractii.in");
	ofstream g("fractii.out");
	f>>n;
	if(n>1)for(i=2;i<=n;i++)s+=fi(i);
	else s=0;
	g<<1+(s<<1);
	return 0;
}