#include <fstream>
#include <cstdlib>
#define N_MAX 1000011

using namespace std;
int phi[N_MAX];
int main( void )
{
	int N, i, j;
	long long int k=1;
	ifstream in( "fractii.in" );
	in>>N;
	for( i=1; i <= N; ++i )
		phi[i]=i;
	for( i=2; i <= N; ++i )
	{
		if( i == phi[i] )
		{
			for( j=i; j <= N; j+=i )
				phi[j]=(phi[j]/i)*(i-1);
		}
		k+=phi[i];
	}
	ofstream out( "fractii.out" );
	out<<(2*k-1)<<'\n';
	return 0;
}