n = int(input())
import math
def is_prime(n):
    if n == 1: return False
    for k in range(2, int(math.sqrt(n)) + 1):
        if n % k == 0:
            return False
    return True

prime = []
for i in range(1, n+1):
    if is_prime(i):
        prime.append(i)

if n == 1:
    print(0)
else:
    ans = 1
    for r in prime[1:]:
        if r**2-2 > n:
            break
        if r**2-2 in prime:
            ans += 2
    print(ans)