input: 
  def count_up_to(n):
      """Implement a function that takes an non-negative integer and returns an array of the first n
      integers that are prime numbers and less than n.
      for example:
      count_up_to(5) => [2,3]
      count_up_to(11) => [2,3,5,7]
      count_up_to(0) => []
      count_up_to(20) => [2,3,5,7,11,13,17,19]
      count_up_to(1) => []
      count_up_to(18) => [2,3,5,7,11,13,17]
      """
  
output:     def is_prime(num):
          if num < 2:
              return False
          for i in range(2, int(num**0.5) + 1):
              if num % i == 0:
                  return False
          return True
  
      primes = []
      for i in range(2, n):
          if is_prime(i):
              primes.append(i)
      return primes