#include <stdio.h>  
    
   #define NMAX 1000000
    
   long N;  
   long long rez;  
     
   long long v[NMAX];  
     
  int main()  
  {  
       freopen("fractii.in", "r", stdin);  
       freopen("fractii.out", "w", stdout);  
     
       long i, j;  
     
       scanf("%ld", &N);  
     
       for(i = 2; i <= N; i++)  
       {  
           v[i] = i-(1+v[i]);  
          for(j = 2; j*i <= N; j++)  
               v[i*j] += v[i];  
       }  
     
      for(i = 2; i <= N; i++)  
           rez +=v[i]*2;  
       rez++;  
     
       printf("%lld\n", rez);  
     
       return 0;  
   }