input: def predict_temperature(temperature_list):
      """
      Predict the next day's forecasted temperature given the past three day's forecasted temperatures using the exponential smoothing algorithm.
      >>> predict_temperature([21, 22, 20])
      20.5
      """
      alpha = 0.5 # Confidence value
      predicted_temperature = temperature_list[-1] # Initializing prediction
      for temperature in temperature_list[:-1]:
          predicted_temperature = alpha*temperature + (1-alpha)*predicted_temperature
      return predicted_temperature
output:     alpha = 0.5  # Confidence value
      predicted_temperature = temperature_list[-1]  # Initializing prediction
      for temperature in temperature_list[:-1]:
          predicted_temperature = alpha * temperature + (1 - alpha) * predicted_temperature
      return predicted_temperature