#include<stdio.h>
#define N 1000000
int n, v[N];
void fractii()
{
	for (int i=1; i<=n; ++i) v[i]=i;
	for (int i=2;i<=n; ++i)
		if (v[i]==i)
			for (int j=i; j<=n; j+=i)
				v[j]=v[j]/i*(i-1);
}
void citire()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d",&n);
	fractii();
	long long s=0;
	for (int i=1; i<=n; ++i)
		s+=v[i];
	s=s*2+1;
	printf("%lld",s-2);
}
int main()
{
	citire();
	return 0;
}