import Control.Monad
import Data.Char
import Data.List
import Data.Maybe


splitOn :: Eq a => a -> [a] -> [[a]]
splitOn c xs = case break (== c) xs of
    (pre, []) -> [pre]
    (pre, _ : post) -> pre : splitOn c post

strip :: String -> String
strip = dropWhile isSpace . reverse . dropWhile isSpace . reverse

swap :: Int -> Int -> [a] -> [a]
swap i j (hd:tl) = case (i, j) of
    (0, _) -> uncurry (:) (go (j-1) hd tl)
    (_, 0) -> uncurry (:) (go (i-1) hd tl)
    (_, _) -> hd : swap (i-1) (j-1) tl
  where
    go 0 v (hd:tl) = (hd, v : tl)
    go k v (hd:tl) = fmap (hd :) (go (k-1) v tl)

data Ins = Spin Int | Exch Int Int | Part Int Int
  deriving Show

newtype State = State [Int]

instance Show State where
    show (State ar) = map (chr . (+ ord 'a')) ar

parse :: String -> Ins
parse ('s' : s) = Spin (read s)
parse ('x' : s) = let [a, b] = splitOn '/' s in Exch (read a) (read b)
parse ['p', a, '/', b] = Part (ord a - ord 'a') (ord b - ord 'a')

exec :: State -> Ins -> State
exec (State ar) (Spin n) = State $ take 16 (drop (16 - n) (cycle ar))
exec (State ar) (Exch i j) = State $ swap i j ar
exec (State ar) (Part a b) =
    let i = fromMaybe (-1) (findIndex (== a) ar)
        j = fromMaybe (-1) (findIndex (== b) ar)
    in State $ swap i j ar

main :: IO ()
main = do
    input <- liftM (map parse . splitOn ',' . strip) (readFile "16.in")
    print (foldl exec (State [0..15]) input)