import math

N = int(input())
if N == 1: print(0)
else:
	prime = []
	numberlist = []
	for i in range(2, N+1):
		numberlist.append(i)
	while numberlist[0] <= int(math.sqrt(N)):
		now = numberlist.pop(0)
		prime.append(now)
		newnumberlist = []
		for i in range(0, len(numberlist)):
			if numberlist[i]%now != 0:
				newnumberlist.append(numberlist[i])
		numberlist = newnumberlist
	prime = prime + numberlist
	sqprime = []
	for i in range(0, len(prime)):
		if prime[i]*prime[i] > 2*prime[-1]: break
		sqprime.append(prime[i]*prime[i])
	cnt = 0
	for i in range(0, len(sqprime)):
		if sqprime[i]-2 in prime:
			if i == 0: cnt += 1
			else: cnt += 2
	print(cnt)