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A large electric car factory is making improvements to its autopilot system and needs your help to implement a program that decides whether car B, which is driving in the middle of two cars A and C, needs to accelerate, decelerate or maintain its current speed. The cars are the same and the autopilot sensors will provide the current position of the rear of the three cars on an imaginable axis. See an example in the figure.


Car B needs to be accelerated if the distance from its rear to the rear of car A is less than the distance from its rear to the rear of car C. If it is greater, it needs to be decelerated. If it's the same, it needs to maintain its current speed.

Input: Three integers (int), which represent the current positions of the backs of cars A, B and C, respectively.

Output: An integer 1 if car B needs to accelerate; -1 if it needs to decelerate; or 0 if it needs to maintain its current speed.


assert speed_adjust(0, 2, 6) == 1
assert speed_adjust(0, 4, 6) == -1
assert speed_adjust(0, 3, 6) == 0


  • A < B < C

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CheckiO Extensions

CheckiO Extensions allow you to use local files to solve missions. More info in a blog post.

In order to install CheckiO client you'll need installed Python (version at least 3.8)

Install CheckiO Client first:

pip3 install checkio_client

Configure your tool

checkio --domain=py config --key=

Sync solutions into your local folder

checkio sync

(in beta testing) Launch local server so your browser can use it and sync solution between local file end extension on the fly. (doesn't work for safari)

checkio serv -d

Alternatevly, you can install Chrome extension or FF addon

checkio install-plugin
checkio install-plugin --ff
checkio install-plugin --chromium

Read more here about other functionality that the checkio client provides. Feel free to submit an issue in case of any difficulties.

Pair Programming (Beta-version)

Welcome to Pair Programming! Engage in real-time collaboration on coding projects by starting a session and sharing the provided unique URL with friends or colleagues. This feature is perfect for joint project development, debugging, or learning new skills together. Simply click 'Start Session' to begin your collaborative coding journey!

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You are trying to join a pair programming session that has not started yet.

Please wait for the session creator to join.

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It looks like the creator of the pair programming session closed the editor window.

It might happen accidentally, so that you can wait for reconnection.

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