#include<fstream>
#include<cstdio>
#define MaxN 1000000
using namespace std;
ifstream f ("fractii.in");
ofstream g ("fractii.out");
int n,v[MaxN];
long long int rez = 0;
int main(void)
{
	f >> n;
	int i,j;
	for( i = 1 ; i <= n ; i++ )
		v[i] = i;
	for( i = 2 ; i <= n ; i++ )
		if( v[i] == i )
			for( j =  i ; j <= n ; j += i )
				v[j] = v[j]/i*(i-1);
	for( i = 1 ; i <= n ; i++ )
		rez += v[i];
	g << rez*2 - 1 << '\n';
	f.close();
	g.close();
return 0;
}