How Many Days To Spend In Cuba?

What is the minimum number of days to spend in Cuba?
Cuba is very rich in attractions of different types: the sea, tropical nature, modern and contemporary history, colonial architecture, tangible and intangible art and culture, popular customs, and social organization.
With such a wealth of options, how not to get lost? How many days must one devote to a trip to Cuba to have the feeling of having tasted at least some features of its essence?