#include <cstdio>
#define nmax 1000000
using namespace std;
FILE *f1, *f2;

long int n,i,j;
long int v[nmax];
long long s=0;
int main()
{
	f1 = freopen("fractii.in", "r", stdin);
	scanf("%li", &n);
	fclose(f1);
	
	for(i=1;i<=n;i++) v[i] = i-1;
	for(i = 2;i<=n; i++){
		s+=v[i];
		for(j = 2*i; j<=n;j+=i)
			v[j] -= v[i];
	}
	
	
	s=2*s+1;
	
	f2 = freopen("fractii.out", "w", stdout);
	printf("%lli\n", s);
	fclose(f2);
	return 0;
}