#include<stdio.h>
const int N=1<<20;
int e[N],i,j,n;
long long s;
int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d",&n);
	for (i=1; i<=n; ++i)
		e[i]=i;
	for (i=2; i<=n; ++i)
		if (e[i]==i)
			for (j=i; j<=n; j+=i)
				e[j]=e[j]/i*(i-1);
	for (i=2; i<=n; ++i)
		s+=e[i];
	printf("%lld",2*s+1);
	return 0;
}