import Data.Maybe
data Tree a = Empty | Node a [Tree a]

depthFirstSearch _ Empty = Nothing
depthFirstSearch needle (Node val children) =
  if needle == val then Just needle
  else let results = dropWhile isNothing $
                               map (depthFirstSearch needle) children
       in if null results then Nothing else head results

main = do
       needle <- getLine
       let tree = Node "a" [Node "b" [Node "d" [Empty], Node "e" [Empty], Node "f" [Empty]], Node "c" [Node "g" [Node "h" [Empty]]]]
       putStrLn $ show $ depthFirstSearch needle tree