#include<fstream.h>

long long a[1000001];
long n,i,j;
long long sum;

int main()
{
	ifstream f("factii.in");
	ofstream g("fractii.out");
	f>>n;
	sum=0;
	for (i=2;i<=n;++i) a[i]=i;
	for (i=2;i<=n;++i)
	if (a[i]==i) 
		{
			for (j=i+i;j<=n;j+=i) 
				{
					a[j]=a[j]/i;
					a[j]=a[j]*(i-1);
				}
			--a[i];
		}
	for (i=2;i<=n;i++)
		sum+=a[i];
	g<<sum*2+1<<"\n";
	f.close();
	g.close();
}