#include<fstream>
#include<iostream.h>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
long long n,i,j,x=0,b[1000002];

int main()
{

	fin>>n;
	for(i=2;i<=n;i++)
	{
		b[i]=i-1;
	}
	for(i=2;i<=n;i++)
	{
		x=x+b[i];
		for(j=i*2;j<=n;j=j+i)
		{
			b[j]=b[j]-b[i];
		}
	}
	x=x*2+1;
	fout<<x;
	fin.close();
	fout.close();
	return 0;
}