def count_primes(n):
    sieve = [True] * (n + 1)
    sieve[0] = sieve[1] = False
    for i in range(2, int(n ** 0.5) + 1):
        if sieve[i]:
            for j in range(i * i, n + 1, i):
                sieve[j] = False
    return sum(sieve)

print(count_primes(100))