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