add Problem 18 #58

	name: Test

	# https://docs.github.com/en/actions/using-jobs/using-concurrency#example-only-cancel-in-progress-jobs-or-runs-for-the-current-workflow
	concurrency:
	group: ${{ github.workflow }}-${{ github.ref }}
	cancel-in-progress: true

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

	jobs:
	build:
	runs-on: ubuntu-latest
	steps:
	- name: checkout
	uses: actions/checkout@v4

	- name: Install elan
	run: \|
	curl https://raw.githubusercontent.com/leanprover/elan/master/elan-init.sh -sSf \| sh -s -- -y --default-toolchain $(cat lean-toolchain)
	echo "$HOME/.elan/bin" >> $GITHUB_PATH

	- name: Check lib completeness
	run: lake exe import_check Src

	- name: Cache dependencies
	uses: actions/cache@v3
	with:
	path: .lake
	key: deps-${{ runner.os }}-${{ hashFiles('lean-toolchain') }}-${{ hashFiles('lake-manifest.json') }}
	restore-keys: \|
	deps-${{ runner.os }}-${{ hashFiles('lean-toolchain') }}

	# If you use mathlib, uncomment it out.
	# - name: get mathlib cache
	# run: lake exe cache get

	- name: run 'lake build'
	run: lake build

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