#include <fstream.h>

ifstream fin("fractii.in");
ofstream fout("fractii.out");

long long unsigned int s=0,a[1000000],j,n,i;

int main()
{   fin>>n;

	for(i=2;i<=n;i++)
		if(!a[i])
		{
			s+=i-1;

			for(j=i*2;j<=n;j+=i)
				if(a[j])	a[j]-=a[j]/i;
				else a[j]=j-j/i;
		}
		else s+=a[i];

	fout<<2*s+1;

	return 0;
}