article "the" needed in this sentence or not
Solution 1:
In the case of plural countable nouns, the the is often optional. It is usual to include it when the noun is defined in some way.
In your case, "the" people is encouraged by "who have to live in the cities" - the noun "people" is defined, and the the in "the cities is encouraged as "cities" is defined by "which they absolutely hate."
This defining allows the use of "the" as "the" (a determiner) is basically a demonstrative adjective closely related to "that/those".
I would therefore include both.