In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. Your answer should be chosen from the given text, and should not contain other words.

Input: Consider Input: Lucky:  I know you 're smart , Spot , but how do you handle pressure ? Solve this simple word problem in say , thirty seconds .
Spot: Ah - ha , no problem ! Two trains are heading toward each other , _ one _ at twenty - five miles an hour and the other at forty . They 're fifty miles apart and getting closer on the same track , but with no time to throw the switch , they collide , head on . All aboard perish and it 's all my fault !
Lucky: Next .

Output: trains


Input: Consider Input: The Doctor:  I 'm sorry to tell you that Romana can look after herself . We 're Time Lords . Not like those innocents on Atrios , you know . Time Lords , sent by the Guardian to recover the Key to Time .
The Shadow: I know who you are , Doctor , I have always known . I have been waiting for you . I too serve a Guardian , a Guardian equal and opposite in power to the _ one _ you serve . The Black Guardian - he who walks in darkness . And you are in the valley of the Shadow !

Output: Guardian


Input: Consider Input: Mike Hammer:  Velda , I do n't like computers .
Velda: Mike , a computer could bring some order to this place , into your life ...
Mike Hammer: I ca n't think of a better reason for not having _ one _ .


Output: computers