`calc` のコード例の誤りを修正 #398

	name: sync exercise and solutions

	concurrency:
	group: ${{ github.workflow }}-${{ github.ref }}
	cancel-in-progress: true

	on:
	pull_request:
	branches:
	- main
	push:
	branches:
	- main
	workflow_dispatch:

	permissions:
	contents: write
	pages: write
	id-token: write

	jobs:
	sync_exercise:
	runs-on: ubuntu-latest
	steps:
	- name: checkout
	uses: actions/checkout@v4
	with:
	ref: ${{ github.event.pull_request.head.ref }}

	- name: Install elan
	run: \|
	curl https://raw.githubusercontent.com/leanprover/elan/master/elan-init.sh -sSf \| sh -s -- -y --default-toolchain none
	echo "$HOME/.elan/bin" >> $GITHUB_PATH

	# ファイル名変更により解答と対応しない演習問題が残ることを避けるため、
	# いったん演習ファイルを全て削除している
	- name: run mk_exercise
	run: \|
	rm -r LeanByExample/Tutorial/Exercise
	lake exe mk_exercise LeanByExample/Tutorial/Solution LeanByExample/Tutorial/Exercise

	- name: detect diff
	id: diff
	run: \|
	git add -N LeanByExample/Tutorial/Exercise
	git diff --name-only --exit-code

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