#include<stdio.h>
#include<math.h>
FILE *f=fopen("fractii.in","r"),
     *g=fopen("fractii.out","w");
int n,i,j,fi,nr,k,i1,nr1;
int main()
{ fscanf(f,"%d",&n);
  nr=2*n-1;
  if(i==2) { if(n%2==0) nr+=(n/2)*2;
	   else nr+=((n/2)+1)*2;
	 }
  for(i=3;i<=n;i++) {
		       fi=i;
		       i1=i;
		       if(i1%2==0) { fi*=1/2;
				 while(i1%2==0) i1/=2;
			         }
		       k=sqrt(i1);

		       for(j=3;j<=k;j=j+2) { if(i1%j==0) fi*=((j-1)/j);
				        while(i1%j==0) i1/=j;
				      }
		       nr1+=fi;

		 }
  nr1=nr1*2;
  nr=nr+nr1;
  fprintf(g,"%d\n",nr);
  fclose(f);
  fclose(g);
  return 0;
}