Creating spreads

Hi guys! Simple proble, I guess someone already solved it:

I wanna create a new spread from two I have:
in the first I have some values
in the second I have the number of occorence of the value in the first

ex. I have (a, b, c) and (3,2,4) the result is
(a, a, a, b, b, c, c, c, c)

ok, it is easy to do with Cons (Spreads), but I don’t know how many elements I have in the first spread! (the second spreads have the same number of elements of the first)

Does this help?

here it is, that little bastard!

:D thank you Hadasi!