leaving two last semigroup exercises for the future
leaving two last semigroup exercises for the future

raventid/coursera_learning,raventid/coursera_learning,raventid/coursera_learning,raventid/coursera_learning,raventid/coursera_learning,raventid/coursera_learning,raventid/coursera_learning,raventid/coursera_learning,raventid/coursera_learning,raventid/coursera_learning