# include <iostream>
# include <stdio.h>
# include <math.h>
//# include <conio.h>
using namespace std;


    
int generate (int n) { 
 int phi[n],i,j;
for (int i=1;i<=n;i++) phi[i]=i;

for (int i=2;i<=n;i++)
   if (phi[i]==i)
      for (j=i;j<=n;j+=i) phi[j] /=i, phi[j] *= (i-1);
int sum = 0;     
for (i = 1 ; i <= n ; i++)
 sum += phi[i];
 return 2*sum - 1;
}



int main () 
{ 
 int n;   
FILE *f,*g; 
f = fopen ("fractii.in","rt");
g = fopen ("fractii.out", "wt");
fscanf(f, "%i", &n);
fprintf(g, "%d", generate (n));
//getch();
 return 0;   
}