One liner ....oracle

I was untangling a query when I came across eight variations of this code where only the literals 'a' to 'e' changed. Two of these were nested within an additional NVL so that the second would execute if the first returned null.

nvl(decode(2, 1, 'a', 2, 'b', 3, 'c', 4, 'd', 5, 'e', ' '), 'na')