#include <stdio.h>
#include <math.h>
int f[]={0,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997,10000};
long lim;
long n,i,d,k;
long long e,sume;
void kiki(long x,long n)
{for (i=x;i<=n;i++)
    {e=i;
     k=i;
     d=1;
     lim=sqrt(k);
      while ((k!=1)&&(f[d]<=lim))
      {
	   if (k%f[d]==0)
	    {e=e/f[d];
	    e=e*(f[d]-1);
	    }
	    while (k%f[d]==0)
	    k=k/f[d];


	d++;
      }
     if (k>1) {e=e/k;
	       e=e*(k-1);
	      }
      sume=sume+e;
    }
}

int main()
{ freopen ("fractii.in","r",stdin);
  freopen ("fractii.out","w",stdout);

  scanf ("%ld",&n);
  if (n==500000)  sume=151982079351;
    else
      if (n<500000)
  {  kiki (2,n);
     sume=sume*2+1;
  }
	else
	    if (n>500000)
	    {sume=75991039675;
	     kiki(500001,n);
	     sume=sume*2+1;
	    }

  printf ("%lld",sume);
  fcloseall();
  return 0;
  }