Filter positions in a list, Haskell

Question

I need to print the elements of odd index. Currently is printing index.

I don't understand how I can print elements of this index?

f :: [Int] -> [Int]
f lst = filter odd [0..length lst]

-- I can't edit this part
main = do
   inputdata <- getContents
   mapM_ (putStrLn. show). f. map read. lines $ inputdata

Answer 1

If you want to do this "on foot":

odds [] = []
odds [x] = []
odds (e1:e2:xs) = e2 : odds xs