Based on the news about the stock in the past five trading days, please predict the rise or fall of the stock in the next trading day. If the stock is predicted to rise in the next trading day, please output [Rise], if the stock is predicted to fall in the next trading day, please output [Decrease].

Date:2020-12-22, Stock:PTR, The news for the past five days is as follows:
2020-12-15: nan
2020-12-16: nan
2020-12-17: nan
2020-12-18: nan
2020-12-21: nan

Answer: Decrease