#include <stdio.h>
FILE *f=fopen("fractii.in","r"),*g=fopen("fractii.out","w");
long long unsigned a[1000000],n,i,j,x,s;
     
int main()      
{
      fscanf(f,"%llu",&n);
    for(i=2;i<=n;++i)
       {if(a[i]==0)
	  s+=i-1;
	else s+=a[i];
       if(a[i]==0)
       for(j=2;i*j<=n;++j)
	if(a[i*j]==0)
	a[i*j]=(i*j)-j;
	else
	a[i*j]-=a[i*j]/i;
       }
      s=s*2+1;
      fprintf(g,"%llu",s);
      fclose(g);
      return 0;      
}