import Data.Array
import Data.List
import Debug.Trace (traceShow)

main :: IO ()
main = do
  input <- readFile "input"
  let ls = lines input
  let map = makeMap ls
  let pos = findStart ls
  let path = walkGuard map pos (-1,0) [pos]
--  print (nub path)
  print (length (nub path))
--  print (grid ! (1,7))

walkGuard map pos dir path =
  if (atEdge map pos) then
    path
  else let front = addPair pos dir
       in if (map ! front) then
            walkGuard map pos (rotRight dir) path
          else
            walkGuard map front dir (front:path)

atEdge map pos =
  let ((miny,minx), (maxy,maxx)) = bounds map
      (y,x) = pos
  in x == minx || x == maxx ||
     y == miny || y == maxy

addPair (x,y) (dx,dy) = (x+dx,y+dy)

rotRight (up,right) = (right,-up)

makeMap :: [String] -> Array (Int, Int) Bool
makeMap grid = array bounds elements
  where n = length grid
        m = length (head grid)
        bounds = ((0,0), (n-1,m-1))
        elements = [((i,j), (grid!!i!!j) == '#') |
                    i <- [0..n-1], j <- [0..m-1]]

findStart grid =
  head [(i,j) | i <- [0..n-1], j <- [0..m-1], grid!!i!!j == '^']
  where n = length grid
        m = length (head grid)