Trying to insert v into a list just before the rightmost item greater than v, or at index 0 if no items are greater than v.

```
def insert(lst,v)

>>> my_list = [3, 10, 4, 2]
>>> insert(my_list, 5)
>>> my_list
[3, 5, 10, 4, 2]

>>> my_list = [4, 3, 2, 1]
>>> insert(my_list, 20)
>>> my_list
[20, 4, 3, 2, 1]

```