How do you solve this Haskell problem?

I want to define a function replicate to replicate a list of numbers by its value using only list comprehension, for example:

replicate [5,1,3,2,8,1,2]output: [5,5,5,5,5,1,3,3,3,2,2,8,8,8,8,8,8,8,8,1,2,2]

I know this would be easy to use the 'replicate' built in function but only list comprehension is allow, how can I do this?

THANKS!