import Data.List

main :: IO ()
main = do
  input <- readFile "input"
  let grid = lines input
  let antennas = getAntennas grid
  let nodes = filter (isInBounds (gridBounds grid) ) .
              nub .
              flatten .
              map getAntinodes .
              groupAntennas $ antennas
  print $ length nodes

isInBounds (h,w) (y,x) = y >= 0 && y < h && x >= 0 && x < w

getAntinodes coords =
  let n = length coords
      node (y1,x1) (y2,x2) = (y2 + y2-y1, x2 + x2-x1)
  in [node (coords!!j) (coords!!i) | j <- [0..n-1], i <- [0..n-1], i /= j]

groupAntennas =
  map (map snd) .
  groupBy (\a b -> fst a == fst b) .
  sortOn fst

flatten l = foldl (++) [] l

gridBounds grid = (length grid, length (head grid))

getAntennas grid =
  let (n,m) = gridBounds grid
  in [(grid!!i!!j, (i,j)) | i <- [0..n-1], j <- [0..m-1], grid!!i!!j /= '.']