#include <fstream>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

long long n,nr=0,i,j,*phi;

int main(){
	fin>>n;
	phi=new long long [n+1];
	for (i=2; i<=n; ++i)
		phi[i]=i-1;
	for (i=2; i<=n; ++i){
		j=2*i;
		while (j<=n){
			phi[j]-=phi[i];
			j+=i;
		}
	}
	for (i=2; i<=n; ++i)
		nr+=phi[i];
	fout<<nr*2+1;
	delete [] phi;
	fin.close();
	fout.close();
	return 0;
}