n = int(input())

def Is_prime(n):
    if n % 2 == 0:
        return False
    i = 3
    while i < int(n ** (0.5))+ 1:
        if n % i == 0:
            return False
    return True

count = 0
for j in range(0,n):
    if Is_prime(n):
        count += 1