#include<stdio.h>  
    int  n,i,j;  
    long long v[1001000],nr;  
    int main( void )  
    {  
      
    FILE * in = fopen("fractii.in", "r");  
    fscanf(in, "%d", &n);  
    fclose(in);  
   for(i = 2;i <= n;i++)  
       v[i] = i - 1;  
   for(i = 2;i <= n;i++)  
       for(j= i + i;j <= n;j += i)  
           v[j] -= v[i];  
   for(i = 2;i <= n; i++)  
       nr += v[i];  
   nr = 2 * nr + 1;  
   FILE * out = fopen("fractii.out", "w");  
   fprintf(out, "%lld", nr);  
   fclose(out);  
   return 0;  
   }