Get the index of an element in a nested list of the upper level list

I would like to retrieve the RED index referred to the upper level of the input list.
I tried several combinations changing the levels and level of depth both keeping the structure or not and I could not find the solution.
I can solve with python, but I would rather upgrade my skills with these nodes for the benefit of others who are not using Python.
I have seen a couple of thread like this one, and another one here to try to have ideas. but no success.
Thanks in advance.

hi @rinaldi.enrico_nhs,

can you explain further? what do you mean by the BLUE circles? can you provide a sample output?

Hello,thank you for the fast reply.
I beg your pardon if that was not 100% clear.
I would like to have the index of Blue circled elements, referred to the upper level of the list, not of their sublist.
As to say now I read 0,-1,-1…
The exact result I want is 0,0,0,…because those elements are in the same index 0 of the first level list.
I hope this is clearer.

That is very confusing.

Can you provide a simple input and show what output you would like from that input?

Thanks for your question.
I would like to read the index of 0,0,0.

is this what you mean?

Great! Exactly. Thanks.
And my first reply to you had a typo…not a sarcasm!.
Really thank you, I used Python for it. But I prefer to understand how to use the Nodes available.