#include <stdio.h>  
 int main()  
 {  
    int n,i,j,e[1000005],s;  
     s=1;  
     FILE *f1,*f2;  
      f1=fopen("fractii.in","r");  
     f2=fopen("fractii.out","w");  
    fscanf(f1,"%d",&n);  
     for(i=1;i<=n;i++)  
    {  
         e[i]=i;  
     }  
      for(i=2;i<=n;i++)  
     {  
           if(e[i]==i)  
           {  
               for(j=i;j<=n;j=j+i)  
                   e[j]=e[j]/i*(i-1);  
           }  
       }  
      for(i=2;i<=n;i++)  
       {  
          s=s+2*e[i];  
    }  
       fprintf(f2,"%d",s);  
       fclose(f1);  
       fclose(f2);  
    
     
      return 0;  
  }