#include <cstdio>
using namespace std;

const int N=1<<20;
int e[N];

int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	int i,j,n;
	long long nr=0;
	scanf("%d",&n);
	
	for(i=2;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=1;i<=n;i++)
		nr+=e[i];
	
	printf("%lld\n",(nr*2)+1);
	
	return 0;
}