Need pl/sql script to track history of changes in a table

Dear all,

I have a table which tracks the changes made in 2 columns as old_value and new_value.

For example

A1 changed to A2, then A2 changed to A3, then A3 changed to A4, then A4 changed to A5.

Now, we need a pl/sql script to show that A1 changed to A5, A2 changed to A5, A3 changed to A5, A4 changed to A5. as the final value now is A5

Since the final value for all A1,A2,A3,A4 is A5.

I want to read from the Existing table and insert into a new table with additional field "Final" ( pls refer attached image)