Hi! I just finished the recursion chapter on the **CS with Python** skill path and just trying to get some practice with some online -quite basic- problems.

On this one, i have to find the sum of the elements in a list, and some elements of the list are lists themselves.

This is where I got:

```
def sum_lst_rec(lst, lst_sum = 0):
if len(lst) == 0:
return lst_sum
if isinstance(lst[0], list):
sub_lst = lst[0]
if len(sub_lst) == 0:
return sum_lst_rec(lst[1:], lst_sum)
lst_sum += sub_lst[0]
return sum_lst_rec(sub_lst[1:], lst_sum)
lst_sum += lst[0]
return sum_lst_rec(lst[1:], lst_sum)
test_lst_2 = [1, 2, [3,4], [5, 6]]
print(sum_lst_rec(test_lst_2))
```

The code runs, but only sums until it encounters the first element that is a list. It sums the elements in that list, but doesnâ€™t go on with the recursion. In this example, it returns `21`

What am I missing?!