// pb003.cpp : Defines the entry point for the console application.
//

//#include "stdafx.h"
#include "stdio.h"

#define MAX 1000001
long prime[MAX] = { 0 };

void GenPrime()
{
	long i, j;
	//for (i = 1; i <= MAX; i++) prime[i] = 0;

	prime[1] = 1;
	prime[2] = 1;
	
	for (i = 2; i <= MAX; i += 2)
	{
		for (j = i * 2; j <= MAX; j += i) prime[j] = 1;
	}
}

long fi(long n) 
{ 
   long result = 0, i; 
   for (i = 2; i <= n / 2; i++) 
	   if (prime[i] == 0) result++;
   return result; 
} 


int main()
{
	FILE *fin = fopen("fractii.in", "rt");
	if (!fin) return 0;

	long n = 0, i;
	fscanf(fin, "%ld", &n);

	fclose(fin);

	long long r = 1;

	for (i = 2; i <=n; i++) r += (fi(i) * 2);

	FILE *fout = fopen("fractii.out", "wt");
	if (!fout) return 0;

	fprintf(fout, "%lld", r);

	fclose(fout);

	return 0;
}