#include<iostream>
#include<fstream>
using namespace std;
int main()
{
	int n,i,j,nr,phi,r=1;
	fstream f("fractii.in",ios::in);
	fstream g("fractii.out",ios::out);
	f>>n;
	for(i=2;i<=n;i++)
	{
		nr=i;phi=nr;
		for(j=2;j*j<=nr;j++)
		{
			if(nr%j==0)
				phi=(phi*(j-1))/j;
			while(nr%j==0)
				nr=nr/j;
		}
		if(nr>1)
			phi=(phi*nr-1)/nr;
		r=r+2*phi;
	}
	g<<r;
}