#include<iostream>
#include<stdio.h>
using namespace std;
 double int prim (long int k)
{ 
	int i,h=0;
for (i=2;i<=k/2;i++)	
if (k%i==0)
	h++;
if (h==0)
	return 1;
else return 0;
}
long int Euler ( long int x)
{
	int i,d=1,c,p=x,a;
	for (i=2;i<=x/2;i++)
		{
			if (x%i==0)
			{a=prim(i);
				if (a==1)
	           { c=i-1; 
				p=p*c/i;
				d=0; } } } 
	
	if (d==1)
p=x-1;
		return p;
}
long int rez (long int m)
{
	int s;
	if (m==1)
		return 1;
		s=2*Euler(m)+rez(m-1);
	return s; 
}
int main ()
{ 
long int n;
FILE* f=fopen("fractii1.txt","r");
FILE* g=fopen("fractii2.txt", "w");
fscanf(f,"%d", &n);
fprintf(g,"%d",rez(n));
fclose(f);
fclose(g);
return 0;
}