#include<fstream.h>
ifstream in("fractii.in");
ofstream out("fractii.out");
int e[1000000];
int main()
{
	int n,i,j;
	long long int nr=0;
	in>>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(j=1;j<=n;j++)
		nr+=e[j];
	out<<nr*2-1;
}