input: def predict_temperature(temperature_list):
      """
      Predicts the next day's forecast temperature using the exponential smoothing algorithm.
      Given a list of the past three day's forecast temperatures, it calculates the predicted temperature.
      
      >>> predict_temperature([21, 22, 20])
      21.0
      >>> predict_temperature([20, 25, 22])
      22.5
      """
      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