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+module Day24A where
+
+import System.Environment (getArgs)
+import Data.List (elemIndex)
+import qualified Data.Map.Strict as M;
+
+-- Types
+
+data Direction = E | SE | SW | W | NW | NE
+  deriving (Eq, Show);
+
+data Colour = White | Black
+  deriving (Eq, Show);
+
+type Coord = (Int, Int, Int);
+type Grid = M.Map Coord Colour;
+
+inverse :: Colour -> Colour
+inverse White = Black
+inverse Black = White
+
+-- Parsing
+parseDirections :: String -> [Direction]
+parseDirections "" = []
+parseDirections ('e':xs) = E : parseDirections xs
+parseDirections ('w':xs) = W : parseDirections xs
+parseDirections ('s':'e':xs) = SE : parseDirections xs
+parseDirections ('s':'w':xs) = SW : parseDirections xs
+parseDirections ('n':'e':xs) = NE : parseDirections xs
+parseDirections ('n':'w':xs) = NW : parseDirections xs
+parseDirections _ = error "Invalid directions"
+
+parseFile :: String -> IO [[Direction]]
+parseFile f = do
+                c <- readFile f;
+                return $ map parseDirections $ lines c;
+
+-- Grid manipulation
+
+flipTile :: Grid -> Coord -> Grid
+flipTile g c = M.insert c (inverse $ M.findWithDefault White c g) g
+
+baseCoord :: Coord
+baseCoord = (0, 0, 0)
+
+followDirections :: Coord -> [Direction] -> Coord
+followDirections c [] = c
+followDirections (x, y, z) (E:ds) = followDirections (x + 1, y - 1, z) ds
+followDirections (x, y, z) (W:ds) = followDirections (x - 1, y + 1, z) ds
+followDirections (x, y, z) (NE:ds) = followDirections (x + 1, y, z - 1) ds
+followDirections (x, y, z) (NW:ds) = followDirections (x, y + 1, z - 1) ds
+followDirections (x, y, z) (SE:ds) = followDirections (x, y - 1, z + 1) ds
+followDirections (x, y, z) (SW:ds) = followDirections (x - 1, y, z + 1) ds
+
+flipByDirections :: [Direction] -> Grid -> Grid
+flipByDirections ds g = flipTile g $ followDirections baseCoord ds
+
+-- Usage: runghc 24a.hs inputs/day24
+main :: IO ()
+main = do 
+        args <- getArgs;
+        ds <- parseFile $ head args;
+
+        let final = foldr flipByDirections M.empty ds;
+        let blacks = M.size $ M.filter (== Black) final;
+        print blacks;
+        return ();
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