input: Write a function to predict the next day's forecast temperature using the exponential smoothing algorithm given the past three day's forecast temperatures. If the input list has fewer than three temperatures, raise a ValueError.
  assert predict_temperature([21, 22, 20])==21
  assert predict_temperature([25, 24, 26])==25
  assert predict_temperature([30, 29, 31])==30
  assert predict_temperature([22, 23, 21])==22
  assert predict_temperature([27, 28, 26])==27
output: def predict_temperature(temps):
      if len(temps) < 3:
          raise ValueError("Input list must contain at least three temperatures")
      return (temps[-1] + temps[-2] + temps[-3]) // 3