List.Getitematindex nested index

Hi, I’m having trouble getting the indexes of the list, from a list with sublists

As shown in the image I want to take certain indices from the list of curves, these indices are the curves that have the lowest value of their z point, so they are the bottom curves wich i need to create walls from them

[Moldaje de link_SUPEREST-VIGAS_v2.0.dyn|attachment]

(upload://dCZb2KIwxhHumgvA1zmX8aqApzD.dyn) (143.5 KB)

Could you show the result of the + and List.MinimumItem nodes ?

of course!

here is two way to solve it

Thanks for your time, but the final result has to be ordered in the same way as the first list, because I have to take those groups of data for each element and assign the same parameters as the original element.

Also, I still get some wrong data

for example for the first beam, index zero, index 3 should be: z = 163200 and index 1 should be: z = 163200, but returns index 1 = 163800

It seems to works with level 3 ?

I hope you all are doing great. My question is how to handle the node List.GetItemAtIndex in case there is a list (at the given index).
Pics are attached to make the question clearer.