#include <stdio.h>
#include <stdlib.h>


int main()  {
	  
	  int i,j,p,q,n,*eulerphi;
	  int pr[168]={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};
	  long long int s;
	  FILE* in=fopen("fractii.in","r");
	  FILE* out=fopen("fractii.out","w");
	
	  fscanf(in,"%d",&n);
	  eulerphi=(int*)(malloc)((n+1)*sizeof(int));
	  
    for(i=1;i<=n;i++)  eulerphi[i]=i-1;
    eulerphi[1]=1;
    for(i=0;i<168;i++)  {
        p=pr[i];
        for(j=p*p;j<=n;j+=p)
            eulerphi[j]=eulerphi[j/p]*(p-1);
        q=p*p;
        for(j=q;j<=n;j+=q)
            eulerphi[j]=eulerphi[j/p]*p;
    }
    s=0;
    for(i=1;i<=n;i++)  s+=eulerphi[i];
	  
	  
	  
	  
	  fprintf(out,"%lld\n",2*s-1);
	  
	  fclose(in);
	  fclose(out);
	
	return 0;
}