re-numbering a list of numbers based on another list of numbers to get a sequential order

I have a list of numbers in a column. They are stops on a truck route. in another column, i have a list of numbers. They are backhauls that are inserted into the route. I need a formula to re-number the stops based on where the backhauls in the route have been inserted. ex:
Stops: (re-numbered): Backhauls:
1 1 4
2 2 5
3 3 7
4 6
5 8
6 9