input: Write a function to determine if any two numbers in a given list add up to a specified sum. If such a pair exists, return True; otherwise, return False.
  
  def two_sum(numbers, given):
      for i in range(len(numbers)):
          for j in range(i+1, len(numbers)):
              if numbers[i] + numbers[j] == given:
                  return True
      return False
  
  assert two_sum([1, 2, 3, 4, 5], 9) == True
  assert two_sum([1, 2, 3, 4, 5], 10) == False
  assert two_sum([], 0) == False
  assert two_sum([10, 20, 30], 20) == False
  assert two_sum([5, 5, 1, 10, 2], 7) == True
output: def two_sum(numbers, given):
      for i in range(len(numbers)):
          for j in range(i+1, len(numbers)):
              if numbers[i] + numbers[j] == given:
                  return True
      return False