input: from typing import List
  
  def three_layer_nn(input_layer: List[float], hidden_layer: List[List[float]], output_layer: List[float]) -> float:
      """ Create a 3-layer artificial neural network and compute the output.
      >>> three_layer_nn([2, 3], [[0.1, 0.4], [0.8, 0.6], [0.3, 0.9]], [0.3, 0.7])
      0.86
      """
output:     hidden_output = [sum(w * x for w, x in zip(hidden_layer[i], input_layer)) for i in range(len(hidden_layer))]
      output = sum(w * h for w, h in zip(output_layer, hidden_output))
      return round(output, 2)