Different Value Every Time Certain Value Appears In Column

I'm putting together some data for a pivot table.

In Column Q I have a list of products. In column E these products are listed a number of time (depends on the number of regions which may change). What I am looking to do is have column A show "1" the first time the item group is in the list, "2" the second time...up to 12. Basically I'm looking to have a month (#1-12) appear in column A next to the item. If there are 3 regions then then each item will appear in the column E list 3 times. I'd like each group of 3 items to have a "1" the first time they appear, "2" the second...etc.

Here's an example....

1 - Item#1
1 - Item#1
1 - Item#1
1 - Item#2
1 - Item#2
1 - Item#2
2 - Item#1
2 - Item#1
2 - Item#1
2 - Item#2
2 - Item#2
2 - Item#2
3 - Item#1
3 - Item#1
3 - Item#1
3 - Item#2
3 - Item#2
3 - Item#2