#include<fstream>
#include<iostream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int main()
{
	
	int *v;
	int n;
	register int i,j;
	long long s=0;
	fin>>n;
	v=new int[n+1];
	for(i=0;i<=n;i++)
		v[i]=i;
	for(i=2;i<=n;i++)
	{
		if(v[i]==i)
		{
			v[i]=v[i]-1;
			for(j=2*i;j<=n;j+=i)
			{
				v[j]=v[j]-v[j]/i;
			}
		}
	}
	for(i=2;i<=n;i++)
	{
		s+=v[i];
	}
	fout<<s*2+1;
	return 0;
}