input: Write a function to return the first n prime numbers using the Sieve of Eratosthenes algorithm. If n is 0, return an empty list. If n is less than 0, return None.
  def first_n_primes(n):
      if n < 0:
          return None
      if n == 0:
          return []
      if n == 1:
          return [2]
      
      sieve_limit = 1000  # Assuming n <= number of primes up to sieve_limit
      primes = sieve_of_eratosthenes(sieve_limit)
      
      return primes[:n]
  
  assert first_n_primes(0) == []
  assert first_n_primes(1) == [2]
  assert first_n_primes(5) == [2, 3, 5, 7, 11]
  assert first_n_primes(-1) == None
output: def first_n_primes(n):
      if n < 0:
          return None
      if n == 0:
          return []
      if n == 1:
          return [2]
      
      sieve_limit = 1000  # Assuming n <= number of primes up to sieve_limit
      sieve = [True] * (sieve_limit + 1)
      sieve[0] = sieve[1] = False
      
      for start in range(2, int(sieve_limit**0.5) + 1):
          if sieve[start]:
              for multiple in range(start*start, sieve_limit + 1, start):
                  sieve[multiple] = False
      
      primes = [num for num, is_prime in enumerate(sieve) if is_prime]
      
      return primes[:n]