#include<stdio.h>
#include<math.h>

int v[1000001];
long int n;
long long int s;

int main()
{
    
    
    FILE *f=fopen("fractii.in","rt");
    fscanf(f,"%ld",&n);
    fclose(f);
    
    long int i,j;
    for(i=1;i<=n;i++)
      v[i]=i;
    
    for(i=2;i<=n;i++)   
     if(v[i]==i) for(j=i;j<=n;j+=i) v[j]=v[j]/i*(i-1);
     
     for(i=1;i<=n;i++)
      s+=v[i];
    
     
    FILE *h=fopen("fractii.out","wt");
    fprintf(h,"%lld",2*s-1);
    fclose(h);
   
      
      
    return 0;
    }