Tableau If Statement

Here is Tableau DataViz (tab "Other Regions")

I am trying to create columns that

(1) explicitly list region

(2) remaining regions come under "Other Regions"

Value for "Other_Region"

If NOT Region="Ontario" or Region="Prarie" or Region="Quebec" or Region="Yukon" Then "Other Regions" Else Region end

Output is not what I expected. It only lists

(1) Ontario

(2) Other Regions

I was also expecting

• Prarie
• Quebec
• Yukon

My actual data has 200+ regions, hence the need for streamlined statement.

Please guide.