#include<fstream.h>
	ifstream f("fractii.in");
	ofstream g("fractii.out");

long sol=1,i,n;
int ind_euler(long i)
	{

float d=2;long aux=i;float pr=aux;
while(aux!=1)
		{
if (aux%(int)d==0)
{pr*=(d-1)/d;
while(aux%(int)d==0&&aux!=1) {aux/=d;}}
	d++;}
return pr;

	}
int main()
{
f>>n;
for(i=n;i>=2;i--)
	sol+=2*ind_euler(i);
g<<sol;
f.close();
g.close();
return 0;
}