#include <fstream.h>

#define nm 1000010
ifstream f("fractii.in");
ofstream g("fractii.out");

char a[nm];
long b[nm],i,n,j;
long long s;

int main()
{
	f>>n;
	f.close();
	for(i=1;i<=n;i++) b[i]=i;
	
	for(i=2;i<=n;i++)
		if(!a[i])
			for(j=i;j<=n;j=j+i)
			{
				 a[j]=1;
				 b[j]=1LL*b[j]*(i-1)/i;
			}
	
	for(i=2;i<=n;i++) s=s+b[i];
	s=s*2+1;
	g<<s;
	g.close();
	return 0;
}