add day03 + format/black #28

	name: Testing

	on: [push]

	jobs:
	testing:
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2
	- name: Set up Python 3.12
	uses: actions/setup-python@v2
	with:
	python-version: "3.12"
	- name: Install dependencies
	run: \|
	python -m pip install --upgrade pip
	pip install -r requirements.txt
	- name: Run doctests
	run: \|
	python -m doctest 2023/*.py
	- name: Run static type check
	run: \|
	python -m mypy --ignore-missing-imports 2023/*.py
	- name: Check format
	uses: psf/black@stable
	with:
	options: "--check --verbose"
	src: "2023/*.py"

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