#include<iostream.h>
#include<fstream.h>
#include<math.h>

int main()
	{
	fstream f("fractii.in",ios::in),g("fractii.out",ios::out);
	int i,j,nr,phi,n,rez=1;
	f>>n;
	for(i=2;i<=n;i++)
		{
		nr=i;phi=i;
		for(j=2;j<=sqrt(nr);j++)
			if(nr%j==0)
				{
				phi*=(j-1)/j;
				while(nr%j==0)
					nr/=j;
				}
		if(nr>1)
			phi*=(nr-1)/nr;
		rez+=2*phi;
		}
	return 0;
	}