#include <stdio.h>
FILE *f=fopen("fractii.in","r"),*g=fopen("fractii.out","w");
long a[1000000],n,i,j,x,s;

int main()
{
      fscanf(f,"%ld",&n);
      for(i=2;i*i<=n;i++)
         for(j=2;i*j<=n;j++)
            a[j*i]=1;
      for(i=n;i>=2;i--)
         { x=i;
         for(j=2;j<=x/2;j++)
            if(x%a[j]==0 && a[j]!=1)
               {
                   x=x/a[j];
                   s+=x*2;
               }
         }
      s++;
      fprintf(g,"%ld",s);
      fclose(g);
      return 0;
}