#include <stdio.h>
#include <math.h>
FILE *f;
long n,i,j,v[10000],d;
long long s;
long long  tot(long a){
     long ss, c;
     c = 1; ss = a; j = 1;
     while((a > v[j]) && (j<=d) ){
      if(a % v[j] ==0){ c = 0; ss = ss / v[j] ; ss = ss * (v[j]  - 1); } j++;}
     
     if(c == 1){ss = ss-1; d++; v[d] = a;}
     return ss;}
int  main(void){ 
 f= fopen("fractii.in", "rt");
 fscanf(f, "%ld", &n);
 fclose(f);
 s = 1;
 for(i=2;i<=n;i++)s = s + 2 * tot(i); 
  f=fopen("fractii.out", "wt");
  fprintf(f,"%lld", s);
  fclose(f);
    return 0;
}