Friday 13th or Black Friday is considered as unlucky day. Calculate how many unlucky days are in the given year.
Find the number of Friday 13th in the given year.
Input: Year as an integer.
Output: Number of Black Fridays in the year as an integer.
checkio(2015) == 3 checkio(1986) == 1
Precondition: 1000 < |year| < 3000
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
(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 --ff
checkio install-plugin --chromium